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PHP II - Apr 2024

To Do

  • Check date of webinar on PHP package developers falling behind release cycles

  • Make sure attendees get a copy of the updated class when it's released

  • Q: Why was the OrderApp not working?

  • A: The Apache/PHP module had to be updated to 8.3

  • A: Also, the pdo_mysql extension had to be installed

  • Q: Do you have a list of regex testing websites?

  • A: I prefer this one as it's mainly for PHP and supports other functions above just preg_match()

  • A: This one is good if you also need to test regexes in other languages:

  • Fix this example:

<?php
$text = 'April 24, 2024 10:15 AM';
$patt = '/^(\w)+?\b(\d)+?.*?(\d){4}(.*?)/';
$repl = '$2 $1 $3 $4';
echo preg_replace($patt, $repl, $text);
  • Here's the working example:
<?php
$text = 'April 24, 2024 10:15 AM';
$pattern = '/^(\w+).*?(\d+).*?(\d{4})(.*?)$/';
$str = preg_replace($pattern, '$2 $1 $3$4', $text);
echo $str;
echo PHP_EOL;

// Actual output: "24 April 2024 10:15 AM"

Homework

https://github.com/s-wild/zend-lab For Fri 26 Apr 2024

  • Lab: Validate an Email Address

For Wed 24 Apr 2024

  • Lab: Prepared Statements
  • Lab: Stored Procedure
  • Lab: Transaction

For Mon 22 Apr 2024

  • Lab: Interfaces
  • Lab: Type Hinting
  • Lab: Build Custom Exception Class
  • Lab: Traits

For Wed 17 Apr 2024

  • Lab: Namespace
  • Lab: Create a Class For Fri 19 Apr 2024
  • Lab: Create an Extensible Super Class
  • Lab: Magic Methods
  • Lab: Abstract Classes (combine with the Super Class lab)

VM Notes

When you first bring up the VM, after a few minutes you'll see a prompt to "Update Software"

  • Select "Yes" and let it run
  • It will take several hours to complete so it's best to let it run overnight. You'll also see a prompt to "Upgrade the OS"
  • Select "No" for this

Accept New Configuration

  • At some point you will be asked if you wish to retain the original php.ini configuration or accept the new. Go ahead and accept the new configuration.

Update Apache PHP Module

  • So far PHP from the command line (PHP-CLI) has been updated.
  • You'll still need to update the PHP Apache module using these commands.
  • Please note that "8.0" is the old version which is configured for Apache on this VM
  • Find the current version of PHP after the update:
php -v
  • Reconfigure the Apache PHP module according to this version.
    • In this example we use "8.3" as the version.
    • Please note that your version may be different so you'll need to adjust the number accordingly
sudo apt-add-repository ppa:ondrej/apache2
sudo apt install -y libapache2-mod-php8.3
sudo a2dismod php8.0
sudo a2enmod php8.3
sudo systemctl restart apache2

Add vhost definition for sandbox

Follow these instructions to add an Apache vhost (virtual host) definition to sandbox in VM to use as a website

  • From a terminal window (command prompt):
    • Run gedit as the root user:
sudo gedit
  • Open the file /etc/hosts
  • Add an entry to the local hosts file to simulate a server named "sandbox"
127.0.0.1 sandbox
  • Save the file
  • Open a new file (press the "+" icon next to "Open")
  • Paste this into the editor:
<VirtualHost *:80>
   ServerName sandbox
   DocumentRoot /home/vagrant/Zend/workspaces/DefaultWorkspace/sandbox
   <Directory /home/vagrant/Zend/workspaces/DefaultWorkspace/sandbox/>
       Options Indexes FollowSymlinks MultiViews
       AllowOverride All
       Require all granted
   </Directory>
</VirtualHost>
  • Save as /etc/apache2/sites-available/sandbox.conf
  • Exit gedit
  • Test the new simulated server
ping -c3 sandbox
  • Enable the new vhost
sudo a2ensite sandbox
  • Restart Apache
sudo systemctl restart apache2
  • Access sandbox from the VM browser: http://sandbox

Install git [OPTIONAL]

  • Open a terminal window and run this command:
sudo apt install -y git

Install php Adminer

  • Download the latest version from https://www.adminer.org/
  • Copy the downloaded file to /var/www/html/adminer.php
    • Open a terminal window
sudo cp ~/Downloads/adminer-xxx-yyy.php /var/www/html/adminer.php
  • To access: http://localhost/adminer.php
    • Host: 127.0.0.1
    • User: vagrant
    • Password: vagrant
    • Database: phpcourse

Other Stuff

Snapshot

  • Be sure to take a snapshot of the VM before you start any of the labs!

System Problem

  • If you see this message: System program problem detected
  • Do this:
sudo rm -r /var/crash*

Resources

Code examples: https://github.com/dbierer/classic_php_examples PHP Road Map: https://wiki.php.net/rfc Where it all started:

Class Notes

Namespaces

Namespace standard: PSR-4

Differences between PHP 7 and 8:

// works in PHP 7 but not 8 (notice the spaces)
namespace This \ Is \ Normal;
// works in PHP 8 but not 7 (notice the key word "list")
namespace This\Is\A\List;

Keyword as is used to resolve ambiguities

<?php
namespace A\B\C {
    class Test
    {
        public $name = 'ABC';
    }
}

namespace X\Y\Z {
    class Test
    {
        public $name = 'XYZ';
    }
}

namespace {
    // if aliases weren't used, you'd get a Fatal Error
    use A\B\C\Test as ATest;
    use X\Y\Z\Test as ZTest;
    $test = new ATest();
    echo $test->name;
}

Autoloader Examples:

Autoloading example:

<?php
spl_autoload_register(function ($class) {
    require_once __DIR__
           . DIRECTORY_SEPARATOR
           . str_replace('\\', DIRECTORY_SEPARATOR, $class)
           . '.php';
});

use Test\Something\{Test,Whatever};
$test = new Test();
var_dump($test->getIterator([1,2,3,4,5]));
$what = new Whatever();
var_dump($what->whatever());

Here's the example from the OrderApp, index.php which is in public:

spl_autoload_register(
    function ($class) {
        $file = str_replace('\\', '/', $class) . '.php';
        require BASE . '/src/' . $file;
    }
);

Other autoloading example:

<?php
function loader($class) {
	echo $class . PHP_EOL;
	$fn = __DIR__ . '/' . str_replace('\\','/',$class) . '.php';
	require_once($fn);
}
spl_autoload_register('loader');

use X\Caller;

$caller = new Caller();
echo $caller->call_Z();
echo PHP_EOL;
echo $caller->call_A();

// actual output:
/*
X\Caller
X\Y\Z\Test
X\Y\Z:X\Y\Z\Test:X\Y\Z\Test::test
X\Y\A\Test
X\Y\A:X\Y\A\Test:X\Y\A\Test::test
*/

"Caller" class

<?php
namespace X;

use X\Y\Z\Test as ZTest;
use X\Y\A\Test as ATest;

class Caller
{
	public function call_Z()
	{
		// enclosing "new" in parentheses creates instance and allows its immediate use
		return (new ZTest())->test();
	}
	public function call_A()
	{
		// alternatively, you can do this:
		$test = new ATest();
		$result = $test->test();
		unset($test);
		return $result;
	}
}

Example of class using constants:

Class example:

<?php
namespace My\Different\Space;

// you can identify PHP classes like this:
use ArrayObject;
class Test
{
    public function test()
    {
        return __NAMESPACE__;
    }
    public function getArrayObject(array $arr)
    {
        // or: use leading backslash:
        return new \ArrayObject($arr);
    }
}

Calling program:

<?php
include __DIR__ . '/Test.php';
use My\Different\Space\Test;

// alternatively, you can do this:
// $test = new \My\Different\Space\Test();

$test = new Test();
echo $test->test();

$arr = [1,2,3,4,5];
$obj = $test->getArrayObject($arr);
var_dump($obj);

Call methods from inside a class: use $this

<?php
class Test
{
    protected string $first = 'fred';
    protected string $last  = 'flintstone';
    public function getFirst()
    {
        return ucfirst($this->first);
    }
    public function getLast()
    {
        return ucfirst($this->last);
    }
    public function getName()
    {
        return $this->getFirst() . ' ' . $this->getLast();
    }
}
$test = new Test();
echo $test->getName();

Example using __construct()

<?php
class UserEntity {
    protected string $firstName;
    protected string $lastName;
    public function __construct($firstName, $lastName) {
        $this->firstName = $firstName ;
        $this->lastName = $lastName ;
    }
    public function getName()
    {
        return $this->firstName . ' ' . $this->lastName;
    }
}

$user[] = new UserEntity('Jack' , 'Ryan');
$user[] = new UserEntity('Monte' , 'Python');
foreach ($user as $obj)
    echo $obj->getName() . "\n";

Constructor argument promotion example:

<?php
class Test
{
    // contructor argument promotion
    // only in PHP 8.0 and above
    public function __construct(public string $first = '', public string $last = '')
    {
        // do nothing
    }
    public function getFirst()
    {
        return ucfirst($this->first);
    }
    public function getLast()
    {
        return ucfirst($this->last);
    }
    public function getName()
    {
        return $this->getFirst() . ' ' . $this->getLast() . "\n";
    }
}
$test1 = new Test('Fred', 'Flintstone');
echo $test1->getName();

$test2 = new Test('Wilma', 'Flintstone');
echo $test2->getName();

var_dump($test1, $test2);

Creation of dynamic properties is now deprecated (soon to be removed)

<?php
class UserEntity
{
    public function __construct(
		protected string $firstName,
		protected string $lastName)
    {
		// do nothing
    }
    public function init()
    {
		$this->time = new DateTime();
    }

}
ini_set('display_errors', 1);
ini_set('error_reporting', E_ALL);

$user1 = new UserEntity('Jack' , 'Ryan');
$user2 = new UserEntity('Monte' , 'Python');
$user1->init();
$user2->init();

var_dump($user1, $user2);

// PHP Deprecated:  Creation of dynamic property UserEntity::$time
// is deprecated in /home/vagrant/Zend/workspaces/DefaultWorkspace/sandbox/test.php on line 12

Example using get_object_vars() to return JSON representation of object properties

<?php

class UserEntity {
    public function __construct(
        public string $firstName,
        public string $lastName
    ) {}
    public function getJson()
    {
        return json_encode(get_object_vars($this), TRUE);
    }
}

$user1 = new UserEntity('Jack' , 'Ryan');
$user2 = new UserEntity('Monte' , 'Python');

echo $user1->getJson();
echo PHP_EOL;
echo $user2->getJson();

Inheritance example:

//             Transportation
//                   $capacity + $passengers
//			Tires					Sea
//			$tires					$rudder
//    Land       Air    			Sailboat Freighter    
//  Car  Truck   PropPlane   Jet
//   etc.

Using parent:: example:

<?php
class Base
{
    protected string $lastName;
    public function __construct(string $lastName)
    {
        $this->lastName = $lastName;
    }
    public function init(string $lastName)
    {
        $this->lastName = $lastName;
	}
    
}
 

class UserEntity extends Base
{
    protected string $firstName;
    public function __construct(string $firstName, string $lastName)
    {
        $this->firstName = $firstName;
        parent::__construct($lastName);
    }
    public function init(string $firstName, string $lastName)
    {
        $this->firstName = $firstName;
        parent::init($lastName);
	}
}
 
// The subclass
class GuestUser extends UserEntity {
    protected string $role;
    public function __construct(string $firstName, string $lastName, $role)
    {
        $this->role = $role;
    }
    public function init(string $firstName, string $lastName)
    {
        parent::init($firstName, $lastName);
	}
}

Practical anonymous class example:

<?php

class UserEntity {
    public function __construct(
        public string $firstName,
        public string $lastName
    ) {}
    public function getData()
    {
        return new class($this->firstName, $this->lastName)
        {
            public function __construct(public string $firstName, public string $lastName)
            {}
            public function getJson()
            {
                return json_encode(get_object_vars($this), TRUE);
            }
            public function getArrayCopy()
            {
                return get_object_vars($this);
            }
        };
    }
}

$user1 = new UserEntity('Jack' , 'Ryan');
$user2 = new UserEntity('Monte' , 'Python');

echo $user1->getData()->getJson();
echo PHP_EOL;
var_dump($user2->getData()->getArrayCopy());

Example of overriding a method:

<?php
class UserEntity {
    protected string|null $firstName;
    public function setFirstName ($firstName) {
        $this->firstName = $firstName;
    }
}

// The subclass
class GuestUser extends UserEntity {
    protected ?string $mi;
    public function setFirstName($firstName, $mi = null) {
        $this->firstName = trim($firstName);
		$this->mi = ($mi ?? '');
    }
}

$user1 = new GuestUser();
$user1->setFirstName('Jack');
$user2 = new GuestUser();
$user2->setFirstName('Monte' , 'P');

var_dump($user1, $user2);

Restrictions when overriding a method:

  • When overriding a method, you can "expand" the data type in the signature
  • But you can't "narrow" it down
  • You are free to add additional arguments as long as you respect the data types of the original args
  • OR ... just remove the data type entirely which frees you from any restrictions
<?php
class Base
{
    public int $a;
    public int $b;
    public function add(int $a, int $b)
    {
        return $a + $b;
    }
}

//
class Whatever extends Base
{
    // this works:
    public function add(int|float $a, int|float $b, int|float $c = 0)
    {
        return $a + $b + $c;
    }
    /*
    // this does *not* work:
    public function add(float $a, float $b, float $c = 0)
    {
        return $a + $b + $c;
    }
    */
}

$what = new Whatever();
echo $what->add(1, 2, 3);

Magic Methods

Example of __toString()

<?php

class UserEntity {
    public function __construct(
        protected string $firstName,
        protected string $lastName) {
    }

    public function __toString(): string {
        return get_class($this);
        // return json_encode(get_object_vars($this), TRUE);
    }
}

$userEntity = new UserEntity('Mark', 'Watney');
//echo $userEntity;

$reflect = new ReflectionObject($userEntity);
echo $reflect;

// NOTE: this is what you'll see in the 1st of Reflection:
// Object of class [ <user> class UserEntity implements Stringable ] {
// This interface is automatically assigned by PHP 8 and above
// as long as you define __toString()

Another example of __toString()

<?php
class Paragraph
{
	public function __construct(public string $text = '') {}
	public function __toString()
	{
		return '<p>' . $this->text . '</p>';
	}
}
class Bold
{
	public function __construct(public string $text = '') {}
	public function __toString()
	{
		return '<b>' . $this->text . '</b>';
	}
}

$text = <<<TAG
This is paragraph 1
This is paragraph 2
This is bold
TAG;

$count = 0;
$html  = '';
foreach (explode("\n", $text) as $line) {
	if ($count++ === 2) {
		$line = new Bold($line);
	}
	echo (new Paragraph($line));
}

// actual output:
// <p>This is paragraph 1</p><p>This is paragraph 2</p><p><b>This is bold</b></p>

In PHP 8, any class that defines __toString() is automatically associated with the Stringable interface

  • Adding this code to the example above:
$reflect = new ReflectionObject($line);
echo $reflect;
  • Here's the output:
Object of class [ <user> class Bold implements Stringable ] {
  @@ /home/vagrant/Zend/workspaces/DefaultWorkspace/sandbox/test.php 10-17

  - Constants [0] {
  }

  - Static properties [0] {
  }

  - Static methods [0] {
  }

  - Properties [1] {
    Property [ public string $text ]
  }

  - Dynamic properties [0] {
  }

  - Methods [2] {
    Method [ <user, ctor> public method __construct ] {
      @@ /home/vagrant/Zend/workspaces/DefaultWorkspace/sandbox/test.php 12 - 12

      - Parameters [1] {
        Parameter #0 [ <optional> string $text = '' ]
      }
    }

    Method [ <user, prototype Stringable> public method __toString ] {
      @@ /home/vagrant/Zend/workspaces/DefaultWorkspace/sandbox/test.php 13 - 16

      - Parameters [0] {
      }
      - Return [ string ]
    }
  }
}

Example of __destruct()

<?php
class Test
{
	public function __construct(public string $name) {}
	public function __destruct()
	{
		echo __METHOD__ . ':' . $this->name . PHP_EOL;
	}
}

$test1 = new Test('AAA');
$test2 = new Test('BBB');
$test3 = new Test('CCC');

function whatever()
{
	$test4 = new Test('DDD');
}
whatever();

$test1 = NULL;

echo __LINE__ . PHP_EOL;

// actual output:
/*
Test::__destruct:DDD
Test::__destruct:AAA
23
Test::__destruct:CCC
Test::__destruct:BBB
*/

Example using __invoke() to turn an object into a super powered anonymous function:

<?php
class ShowsJson
{
	public function __invoke(array $arr)
	{
		return json_encode($arr, JSON_PRETTY_PRINT);
	}
}

class ShowsHtml
{
	public function __invoke(array $arr)
	{
		$html = '<ul>';
		foreach ($arr as $value) $html .= '<li>' . $value . '</li>';
		$html .= '</ul>';
		return $html;
	}
}

$json = new ShowsJson();
$html = new ShowsHtml();

echo $json(['AAA','BBB','CCC']);
echo PHP_EOL;
echo $html(['AAA','BBB','CCC']);
echo PHP_EOL;

Using __get() to give you the ability to read a protected, but you are unable to write to the property

  • Effectively, this is a read-only property!
  • NOTE: readonly properties were introduced in PHP 8.3
<?php
class UserEntity {
    public function __construct(
        protected string $firstName,
        protected string $lastName
    ) {}

    // Returns an inaccessible property
    public function __get($value) {
        return $this->$value ?? NULL;
    }
}

$userEntity = new UserEntity('Mark', 'Watney');
echo $userEntity->firstName;
$userEntity->firstName = 'Fred';

// Actual output:
// MarkPHP Fatal error:  Uncaught Error: Cannot access protected property

Example using __set() as a "dropbox" where you can write the value but not read it

  • NOTE: it's recommended to not use this to assign dynamic properties as this feature is deprecated
<?php
ini_set('display_errors',1);
ini_set('error_reporting', E_ALL);
class DropBox
{
	protected $values = [];
    public function __set(string $name, mixed $value)
    {
        $this->values[$name] = $value;
    }
}
$drop = new DropBox();
$drop->key1 = bin2hex(random_bytes(8));
$drop->key2 = bin2hex(random_bytes(8));
$drop->key3 = bin2hex(random_bytes(8));
$drop->key4 = bin2hex(random_bytes(8));

var_dump($drop);

echo $drop->values['key1']; // Fatal Error

Serialization example:

<?php
class UserEntity
{
    public $status = ['A','B','C'];
    public function __construct(
        protected string $firstName,
        protected string $lastName,
        protected float $balance,
        protected int $id
    ) {}
    public function getFullName()
    {
        return $this->firstName . ' ' . $this->lastName;
    }
}
$user = new UserEntity('Fred', 'Flintstone', 999.99, 101);
$text = serialize($user);
//$text = json_encode($user);
echo $text . "\n";
$obj = unserialize($text);
//$obj = json_decode($text);
echo $obj->getFullName() . "\n";
var_dump($obj);

Example of __sleep() and __wakeup()

<?php
class UserEntity
{
    public function __construct(
        protected string $firstName,
        protected string $lastName,
        protected float $balance,
        protected int $id,
        protected string $creditCardNum
    ) {}
    public function getFullName()
    {
        return $this->firstName . ' ' . $this->lastName;
    }
    public function getJson()
    {
		return json_encode(get_object_vars($this));
	}
	public function __sleep()
	{
		$_SESSION['cc'] = $this->creditCardNum;
		return ['firstName','lastName','balance','id'];
	}
	public function __wakeup()
	{
		$this->creditCardNum = $_SESSION['cc'] ?? '';
	}
}
session_start();
$user = new UserEntity('Fred', 'Flintstone', 999.99, 101, '1111-2222-3333-4444');
$text = serialize($user);
//$text = $user->getJson();
echo $text . "\n";
$obj = unserialize($text);
//$obj = json_decode($text);
echo $obj->getFullName() . "\n";
var_dump($obj);

Another Example of __sleep() and __wakeup()

<?php
class UserEntity {
    public $hash = '';
    public function __construct(
        protected string $firstName,
        protected string $lastName)
    {
        $this->hash = bin2hex(random_bytes(8));
    }
    public function __sleep()
    {
        return ['firstName','lastName'];
    }
    public function __wakeup()
    {
        $this->hash = bin2hex(random_bytes(8));
    }
    public function getFullName()
    {
        return $this->firstName . ' ' . $this->lastName;
    }
    public function getNativeString(): string {
        return serialize($this);
    }
}
$userEntity = new UserEntity('Mark', 'Watney');
var_dump($userEntity);
echo PHP_EOL;

$native = $userEntity->getNativeString();
$obj  = unserialize($native);
echo $native;
echo PHP_EOL;
var_dump($obj);

Example of __serialize() and __unserialize()

<?php
class UserEntity {
    public $hash = '';
    public function __construct(
        protected string $firstName,
        protected string $lastName)
    {
        $this->hash = bin2hex(random_bytes(8));
    }
    public function __serialize()
    {
        return [
            'firstName' => $this->firstName,
            'lastName' => $this->lastName,
            'sleep_date' => date('Y-m-d H:i:s')];
    }
    public function __unserialize($array)
    {
        // $array contains values restored from the serialization
        $this->hash = bin2hex(random_bytes(8));
        $this->firstName = $array['firstName'];
        $this->lastName = $array['lastName'];
    }
    public function getFullName()
    {
        return $this->firstName . ' ' . $this->lastName;
    }
    public function getNativeString(): string {
        return serialize($this);
    }
}
$userEntity = new UserEntity('Mark', 'Watney');
var_dump($userEntity);
echo PHP_EOL;

$native = $userEntity->getNativeString();
$obj  = unserialize($native);
echo $native;
echo PHP_EOL;
var_dump($obj);

Same example as above except that it encrypts a CC number before serialization

<?php
class UserEntity
{
	protected string $key = '';
	protected string $iv  = '';
    public function __construct(
        protected string $firstName,
        protected string $lastName,
        protected string $ccNum)
    {
		$this->key  = substr(bin2hex(md5(rand(0,999999))), 0, 32);
		$this->iv   = substr(bin2hex(md5(rand(0,999999))), 0, 32);
    }
    public function __serialize()
    {
		$_SESSION['key'] = $this->key;
		$_SESSION['iv']  = $this->iv;
        return [
            'firstName' => $this->firstName,
            'lastName'  => $this->lastName,
            'ccNum'     => base64_encode(
				openssl_encrypt(
					$this->ccNum,
					'aes-256-ctr',
					$this->key,
					0,
					substr($this->iv, 0, 16)
				)
			),
            'sleep_date' => date('Y-m-d H:i:s')];
    }
    public function __unserialize($array)
    {
        // $array contains values restored from the serialization
		$this->key = $_SESSION['key'];
		$this->iv  = $_SESSION['iv'];
        $this->ccNum = openssl_decrypt(base64_decode($array['ccNum']), 'aes-256-ctr', $this->key, 0, substr($this->iv, 0, 16));
        $this->firstName = $array['firstName'];
        $this->lastName = $array['lastName'];
    }
    public function getFullName()
    {
        return $this->firstName . ' ' . $this->lastName;
    }
    public function getNativeString(): string {
        return serialize($this);
    }
}
$userEntity = new UserEntity('Mark', 'Watney', '1111-2222-3333-4444');
var_dump($userEntity);
echo PHP_EOL;

$native = $userEntity->getNativeString();
$obj  = unserialize($native);
echo $native;
echo PHP_EOL;
var_dump($obj);

Example of when getters and setters are useful:

class Test
{
    protected $date;
    const DEFAULT_FMT = 'Y-m-d H:i:s';
    // use getters and setters if there's a need for further processing
    public function setDate(string $str) : void
    {
        $this->date = new DateTime($str);
    }
    public function getDate(string $fmt = self::DEFAULT_FMT) : string
    {
        return $this->date->format($fmt);
    }
}

Example of controlled unlimited properties

<?php
class Test
{
    public const FIELDS = ['fname','lname','balance'];
    public $vars = [];
    // Returns an inaccessible property
    public function __set($key, $value) {
        if (in_array($key, self::FIELDS)) {
            $this->vars[$key] = $value;
        }
    }
    public function __get($key) {
        return $this->vars[$key] ?? '';
    }
}

$test = new Test();
$test->fname = 'Fred';
$test->lname = 'Flintstone';
$test->balance = 999.99;
$test->doesNotExist = 'TEST';
echo $test->fname . ' ' . $test->lname
     . ' has a balance of ' . $test->balance
     . ' and ' . $test->doesNotExist;

Other examples of magic methods:

Three important magic methods not covered in the slides

Example of Abstract class with abstract method:

Examples of classes with interfaces:

Interface example:

<?php
interface ServiceInterface {
    public function getService(string $key);
    public function setService(string $key, callable $service);
}
interface TestInterface {
    public function getTest(string $key);
}
abstract class AbstractController implements ServiceInterface {
    public const FORMAT = 'l, d M Y H:i:s';
    protected array $services = [];
}
class MvcController extends AbstractController
{
    public function getService(string $key)
    {
        return $this->services[$key] ?? NULL;
    }
    public function setService(string $key, callable $service)
    {
        $this->services[$key] = $service;
    }
}
// NOTE: TestInterface mandates `getTest(string $whatever)`
//       and inserts itself into the hierarchy at this point.
//       The effect is seen from this point on down the inheritance hierarchy
class TestController extends MvcController implements TestInterface
{
	public function getTest(string $whatever)
	{
		return $whatever;
	}
}


$callback = new class () {
    protected $date = NULL;
    public function __construct()
    {
        $this->date = new DateTime('now');
    }
    // NOTE: by defining `__invoke()` the anonymous class is now considered "callable"
    public function __invoke()
    {
        return $this->date->format(AbstractController::FORMAT);
    }
};

$controller = new TestController();
$controller->setService('date', $callback);
echo $controller->getService('date')();

Interfaces can be implemented at any level within an inheritance structure

  • They act as "pseudo" superclass
  • They are not tied to specific level within the inheritance tree
<?php
interface HashInterface
{
	public function generateHash(string $key) : string;
}
abstract class AbstractUser implements HashInterface
{
	public function __construct(public string $fname, public string $lname) {}
}

class OldStyleUser extends AbstractUser
{
	public function generateHash(string $key) : string
	{
		return md5($key);
	}
}

class NewStyleUser extends AbstractUser
{
	public function generateHash(string $key) : string
	{
		return password_hash($key, PASSWORD_DEFAULT);
	}
}

$old = new OldStyleUser('Fred', 'Flintstone');
$new = new NewStyleUser('George', 'Jetson');

//echo $old->generateHash('password');
echo PHP_EOL;
echo $new->generateHash('password');
echo PHP_EOL;

This example demonstrates using an interface as a type hint

  • Both Boss and Underling as well as Whatever work as arguments to do_addition() because they implement the correct interface.
<?php
interface AddInterface
{
	public function add(int $a, int $b) : int;
}

class Boss implements AddInterface
{
	public function add(int $a, int $b) : int
	{
		return $a + $b;
	}
}

class Underling extends Boss
{}

class Whatever implements AddInterface
{
	public function add(int $a, int $b) : int
	{
		return $a + $b;
	}
}


function do_addition(AddInterface $obj, $a, $b)
{
	return $obj->add($a, $b);
}

$obj = new Boss();
echo do_addition($obj, 2, 2);

$obj = new Underling();
echo do_addition($obj, 2, 2);

$obj = new Whatever();
echo do_addition($obj, 2, 2);

Example of type hinting

<?php
// if activated: Fatal Error occurs on line 13
// declare(strict_types=1);
class Test
{
	public function add(int $a, int $b) : int
	{
		return $a + $b;
	}
}

$test = new Test();
echo $test->add(5.55, 6.66);	// output: 11
echo PHP_EOL;

echo $test->add(5, 6);			// output: 11
echo PHP_EOL;

echo $test->add('5', '6');		// output: 11
echo PHP_EOL;

echo $test->add('5x', 'x6');	// output: Fatal Error
echo PHP_EOL;

Example of "type widening"

  • The subclass can have a data type that's "wider" than the super class
<?php
interface TestInterface
{
    public function doIterate(array $arr) : string;
}

class Test implements TestInterface
{
    // you could also use "iterable" as a data type
    // which is a combo of array|Traversable
    public function doIterate(iterable $arr) : string
    {
        $output = '';
        foreach ($arr as $item) $output .= $item . PHP_EOL;
        return $output;
    }
}

$test = new Test();
$arr = range('A','F');
echo $test->doIterate($arr);
echo $test->doIterate(new ArrayIterator($arr));

Examples of what is callable

<?php
function cmp($a, $b)
{
    if ($a == $b) {
        return 0;
    }
    return ($a < $b) ? -1 : 1;
}

$anon = function ($a,$b) {
    if ($a == $b) {
        return 0;
    }
    return ($a < $b) ? -1 : 1;
};

$class = new class() {
    public function __invoke($a,$b)
    {
        if ($a == $b) {
            return 0;
        }
        return ($a < $b) ? -1 : 1;
    }
};

$a = array(3, 2, 5, 6, 1);

usort($a, $class);

foreach ($a as $key => $value) {
    echo "$key: $value\n";
}
  • Another example of what is considered callable:
<?php

class Test {
    public function callIt(callable $callback, array $params) {
        return $callback($params);
    }
}

$operands[0] = 2;
$operands[1] = 3;
$callback = function ($p) {
    return 'The result of '
           . $p[0] . ' times ' . $p[1]
           . ' is ' . ($p[0] * $p[1]);
};

$anon = new class() {
    public function __invoke(array $params)
    {
        return 'The sum is: ' . array_sum($params);
    }
};

$stat = new class() {
    public function sum(array $params)
    {
        return 'The sum is: ' . array_sum($params);
    }
};

class Whatever
{
    public static function sum(array $params)
    {
        return 'The sum is: ' . array_sum($params);
    }
}


$test = new Test;
echo $test->callIt($callback, $operands);
echo PHP_EOL;
echo $test->callIt('array_sum', $operands);
echo PHP_EOL;
echo $test->callIt($anon, $operands);
echo PHP_EOL;
echo $test->callIt([$stat, 'sum'], $operands);
echo PHP_EOL;
echo $test->callIt('Whatever::sum', $operands);

gType int can "widen" to float without any loss of precision

<?php
declare(strict_types=1);
class Test
{
    public function add(float $a, float $b)
    {
        return 'The sum is: ' . ($a + $b);
    }
}

$test = new Test();
// still works OK: int --> float doesn't lose precision
echo __LINE__ . ':' . $test->add(2, 2);
echo PHP_EOL;
echo __LINE__ . ':' . $test->add(2.555, 2.666);
echo PHP_EOL;

If declare(strict_types=1) is not in effect, it does a soft typecast

<?php
//declare(strict_types=1);
class Test
{
    public function add(float $a, float $b) : float
    {
        return $a + $b;
    }
}

$test = new Test();
// works OK
echo __LINE__ . ':' . $test->add(2, 2);
echo PHP_EOL;

// works OK
echo __LINE__ . ':' . $test->add(2.555, 2.666);
echo PHP_EOL;

// works OK
echo __LINE__ . ':' . $test->add('2.555', '2.666');
echo PHP_EOL;

// Fatal Error
echo __LINE__ . ':' . $test->add('x2.555', 'x2.666');
echo PHP_EOL;

Example of going from a specific data type to a more general data type

<?php
interface Foo {
    public function test(array $input);
}

class Bar implements Foo {
    // type omitted for $input
    public function test(iterable $input) {
        $text = '';
        foreach($input as $item) $text .= ' ' . $item;
        return 'You requested ' . trim($text);
    }
}

$bar = new Bar();
echo $bar->test(['A','B','C']);
echo $bar->test(new ArrayIterator(['A','B','C']));
  • Using static to get an instance of the lowest level in inheritance tree
<?php
class Foo
{
    public function whatever()
    {
        return 'Whatever';
    }
    public function getInstance() : static
    {
        // this returns an error:
        // return new self();
        return new static();
    }
}
class Bar extends Foo {}

$foo = new Foo();
$bar = new Bar();
var_dump($foo->getInstance());    // Foo
var_dump($bar->getInstance());    // Bar

Using static to "float down" to the lowest inheritance level

<?php
class Foo
{
	public string $name = 'Fred Flintstone';
    public function getInstance(): static
    {
        return new static();
    }
}

class Bar extends Foo
{}

class Baz extends Bar
{}


$foo = new Foo();
var_dump($foo->getInstance());

$bar = new Bar();
var_dump($bar->getInstance());

$baz = new Baz();
var_dump($baz->getInstance());

// Actual Output
/*
 * object(Foo)#2 (1) {
  ["name"]=>
  string(15) "Fred Flintstone"
}
object(Bar)#3 (1) {
  ["name"]=>
  string(15) "Fred Flintstone"
}
object(Baz)#4 (1) {
  ["name"]=>
  string(15) "Fred Flintstone"
}
*/

Typical example using Exception

<?php
class Test
{
	/**
	 * Divide two numbers
	 *
	 * @throws Exception if division by zero
	 * @param float $a
	 * @param float $b
	 * @return float $a / $b
	 */
	public function divide(float $a, float $b) : float
	{
		if ($b == 0) {
			throw new Exception('Cannot divide by zero!');
		}
		return $a / $b;
	}
}

// this is the calling code, and is most likely
// found someplace else in the application:
try {
	$test = new Test();
	echo $test->divide(22, 0);
	echo PHP_EOL;
} catch (Exception $e) {
	error_log(__FILE__ . ':' . __LINE__ . ':' . $e->getTraceAsString());
	echo $e->getMessage();
}

Exception / Error example:

<?php
try {
    $pdo = new PDO('sqlite://xyz');
} catch (PDOException $a) {
    // catches PDOException
    echo __LINE__ . ':' . get_class($a) . ':' . $a . "\n";
} catch (Exception $a) {
    echo __LINE__ . ':' . get_class($a) . ':' . $a . "\n";
} catch (Error $a) {
    echo __LINE__ . ':' . get_class($a) . ':' . $a . "\n";
}

try {
    $pdo = new PDO();
} catch (PDOException $a) {
    echo __LINE__ . ':' . get_class($a) . ':' . $a . "\n";
} catch (Exception $a) {
    echo __LINE__ . ':' . get_class($a) . ':' . $a . "\n";
} catch (Error $a) {
    // catches Error
    echo __LINE__ . ':' . get_class($a) . ':' . $a . "\n";
}
// actual output:
/*
6:PDOException:PDOException: SQLSTATE[HY000] [14] unable to open database file in C:\Users\ACER\Repos\classic_php_examples\oop\test.php:3
Stack trace:
#0 C:\Users\ACER\Repos\classic_php_examples\oop\test.php(3): PDO->__construct()
#1 {main}
21:ArgumentCountError:ArgumentCountError: PDO::__construct() expects at least 1 argument, 0 given in C:\Users\ACER\Repos\classic_php_examples\oop\test.php:14
Stack trace:
#0 C:\Users\ACER\Repos\classic_php_examples\oop\test.php(14): PDO->__construct()
#1 {main}
*/

Using static for a registry style storage class

class Registry
{
	public static $items = [];
	public static function set(string $key, mixed $value)
	{
		static::$items[$key] = $value;
	}
	public static function get(string $key)
	{
		return static::$items[$key] ?? NULL;
	}
}

Registry::set('name', 'Doug Bierer');
Registry::set('array', range('A','F'));

// do something

foreach (Registry::get('array') as $item) {
	echo $item . ':' . Registry::get('name') . PHP_EOL;
}

Other examples of static and traits

Simple Trait example

<?php
trait TestTrait
{
    public function test()
    {
        return 'TRAIT';
    }
}

class Top
{
    use TestTrait;
}

class Child extends Top
{
}

$top = new Top();
$child = new Child();

echo $top->test();
echo PHP_EOL;
echo $child->test();

Example of nested objects:

<?php
class Address
{
	public function __construct(
		public string $streetAddress,
		public string $city,
		public string $postCode,
		public string $country) {}
}

class User
{
	public function __construct(
		public string $name,
		public string $email,
		public Address $address) {}
}

$user = new User(
	'Fred Flintstone',
	'fred@slate_and_granite.com',
	new Address(
		'201 Cobblestone Lane',
		'Bedrock',
		'00000',
		'Unknown')
);

// how to get the city from User
echo $user->name . ' lives in the city of ' . $user->address->city;
echo PHP_EOL;

var_dump($user);

PDO

Example of a generic database class with built-in methods for INSERT, SELECT, UPDATE, DELETE

<?php
try {
    // Get the connection instance
    $pdo = new PDO('mysql:host=localhost;dbname=phpcourse','vagrant','vagrant',
        [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);
 
    // Hard coded input parameters
    $fname = 'Mark';
    $lname = 'Watney';
 
    // We can safely use `exec()` because the stored procedure is an INSERT 
    // and we are only concerned with the number of rows affected
    if ($pdo->exec(sprintf('CALL newCustomer (%s,%s)', $fname, $lname)) {
        echo "New user $fname  $lname added";
    }
} catch (PDOException $e){
    //Handle error
}

Adding options as 4th argument:

try {
    // Get the connection instance
    $opts = [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION];
    $pdo = new PDO('mysql:host=localhost;dbname=phpcourse', 'vagrant', 'vagrant', $opts);
    // Statements ...
} catch (PDOException $e ){
    // Handle exception...
}

To find the exact DSN for a given database in PDO, look at the Driver class documentation

try {
    // Execute a one-off SQL statement and get a statement object
    $stmt = $pdo->query('SELECT * FROM orders');

    // Returns an associative array indexed by column name
    while ($row = $stmt->fetch(PDO::FETCH_ASSOC) {
        // do something with the resulting row
    }

} catch (PDOException $e){
    //Handle error
}

You can use PDO::quote() to manually provide parameter escaping:

<?php
$pdo = /* some PDO instance */
$id  = (int) ($_GET['id'] ?? 0);
$id  = ($id < 0) ? 0 : $id;
// assuming $id is sanitized, quote() can be used to manually provide platform quoting
$sql = 'SELECT id, first, last FROM users WHERE id=' . $pdo->quote($id);

Alternative way to execute without using bindParam()

$data = [
    'eventTitle' => 'Wagner, Bryant',
    'eventURL' => 'http://bryant.prestosports.com/sports/bsb/2021-22/schedule#6irpaohben8y4ati',
    'eventDescription' => 'Baseball on May 21, 2022 at 3:00 PM: Wagner, Bryant, Conaty Park',
    'eventCategory' => 'Baseball',
    'eventDateString' => 'Sat, 21 May 2022 19:00:00 GMT',
    'eventGUID' => 'http://bryant.prestosports.com/sports/bsb/2021-22/schedule#6irpaohben8y4at',
    'eventOpponent' => 'Wagner',
];
$stmt->execute($data);

Example of PDO::FETCH_CLASS mode:

<?php
class Order
{ }

$conf= [
	'dsn' => 'mysql:unix_socket=/var/run/mysqld/mysqld.sock;dbname=phpcourse',
	'username' => 'vagrant',
	'password' => 'vagrant',
	'options'  => [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION],
];

try {
	$pdo = new PDO($conf['dsn'], $conf['username'], $conf['password'], $conf['options']);

    // Execute a one-off SQL statement and get a statement object
    $stmt = $pdo->query('SELECT * FROM orders');
	$stmt->setFetchMode(PDO::FETCH_CLASS, 'Order');

    // Returns an instance of Order, one row at a time
    while ($result = $stmt->fetch()) {
		var_dump($result);
	}
} catch (PDOException $e){
    //Handle error
}

// partial output:
/*
object(Order)#3 (6) {
  ["id"]=>
  int(7)
  ["date"]=>
  string(10) "1360796400"
  ["status"]=>
  string(4) "open"
  ["amount"]=>
  int(300)
  ["description"]=>
  string(24) "A big box of chocolates."
  ["customer"]=>
  int(3)
}
*/

Output Buffering

To start output buffering automatically, in the php.ini file:

// sets buffer size to 4K + activates it
output_buffering=4096

Email

Headers can include any valid headers as per RFC 2822

Regex

Simple example finds all files that start with "Test" and end with "php"

<?php
$str = [
	'Test.php',
	'Test.jpg',
	'Test2.php',
	'Test2.png',
	'No_Test.php',
];

// or you can use this:
// $patt = '/\ATest.*php\Z/';

$patt = '/^Test.*php$/';

foreach ($str as $item) {
	if (preg_match($patt, $item)) {
		$found = 'Found';
	} else {
		$found = 'Not Found';
	}
	echo $item . ' was ' . $found . PHP_EOL;
}

Matches a Canadian postal code

<?php
$text = 'A2A 3B4';
$patt = '/^\w\d\w \d\w\d$/';
preg_match($patt, $text, $match);

var_dump($match);

Alternatives to finding chars at beginning or end of a string:

<?php
$str = '/home/doug/whatever/';

// Any PHP above 4
echo ($str[0] ==='/') ? 'Y' : 'N';
echo ($str[-1] ==='/') ? 'Y' : 'N';

// PHP 8
echo (str_starts_with($str,'/')) ? 'Y' : 'N';
echo (str_ends_with($str,'/')) ? 'Y' : 'N';

Examples using sub-patterns

<?php
$str = '<p>One</p><p>Two</p><p>Three</p>';
$pat = '/<p>(.*?)<\/p>/';
preg_match_all($pat, $str, $match);
var_dump($match);


$str = 'Click here to go to <a target="_blank" href="http://zend.com/">Zend</a>!';
$pat = '/<a.*?href=("|\')(.*?)("|\').*?>/';
preg_match_all($pat, $str, $match);
var_dump($match);

Using "dollar" notation to replace the order of subpatterns

<?php
$str = 'Flintstone, Fred';
$pat = '/([A-Za-z]+?), ([A-Za-z]+)/';
$rep = '$2 $1';
echo preg_replace($pat, $rep, $str);
// Actual output: "Fred Flintstone"

Example email validation

<?php
$email = [
    '[email protected]',
    '[email protected]',
    '[email protected]',
    '[email protected]',
    '[email protected]',
    'invalid&/*@company',
    '[email protected]',
];
$pattern = '/^[a-z][a-z0-9.-]*@([a-z0-9]+\.)+[a-z]{2,4}$/i';
foreach ($email as $item) {
    echo $item . ' [';
    echo (preg_match($pattern, $item)) ? 'VALID' : 'INVALID';
    echo ']' . PHP_EOL;
}

Example of searching for a specific file name pattern in a directory

<?php
$list = scandir(__DIR__);
var_dump($list);
$pattern = '/^[\w].*?\.php$/';
foreach ($list as $item) {
    echo $item . ': ';
    preg_match($pattern, $item, $match);
    echo (!empty($match[0])) ? 'MATCH' : 'NO MATCH';
    echo PHP_EOL;
}

// or
var_dump(preg_grep($pattern, $list));

Misc examples

<?php
$data = [
    '/^[A-Z].*/'     => ['The quick brown fox', '12345'],
    '/.*(jpg|png)$/' => ['image.png', 'info.php'],
    '/\bERROR\b/'    => ['ERROR 309: undefined error','This contains ERROR_REPORTING'],
    '/^[A-Za-z ]*$/'  => ['The quick brown fox', '9977 quick brown foxes'],
    '/^[^A-Za-z]*$/' => ['997799989887777','The quick brown fox'],
    '!^http(s)?://\w*!i' => ['https://zend.com','http://sandbox','ftp://whatever.com'],
];

foreach ($data as $pattern => $value) {
    foreach ($value as $item) {
        echo "Testing $item\n";
        echo (preg_match($pattern, $item)) ? 'MATCH' : 'NO MATCH';
        echo PHP_EOL;
    }
}

Shows the use of "?" to indicate an optional "s"

<?php
$list = [
    'http://zend.com',
    'https://www.perforce.com',
    'ftp://unlikelysource.com',
    'file:///some/path/to/file',
];
// searches for http:// or https://
$pattern = '!^https?://\w*!i';
foreach ($list as $item) {
    echo $item . ': ';
    preg_match($pattern, $item, $match);
    echo (!empty($match[0])) ? 'MATCH' : '';
    echo PHP_EOL;
}

Example of preg_replace()

<?php
$test = '<script>alert("test");</script>';
$pattern = ['/</','/>/','/;/'];

echo preg_replace($pattern, '', $test);
echo PHP_EOL;
// output: "scriptalert("test")/script"

$test = '$script{"alert"} = "script"';
$pattern = ['/{/','/}/'];
$replace = ['[', ']'];
echo preg_replace($pattern, $replace, $test);
// $script["alert"] = "script"

Example using sub patterns:

<?php
$str = '<a href="https://zend.com">Zend Website</a>';
$pat = '/<a href="(.*?)">(.*?)<\/a>/';
preg_match($pat, $str, $match);
var_dump($match);

// actual output:
/*
array(3) {
  [0]=>
  string(43) "<a href="https://zend.com">Zend Website</a>"
  [1]=>
  string(16) "https://zend.com"
  [2]=>
  string(12) "Zend Website"
}
*/

Example using preg_replace()

<?php
$text = '<script>Bad Javascript</script>';
$pattern = '![^A-Za-z0-9 ]!';
$str = preg_replace($pattern, ' ', $text);
echo $str;
echo PHP_EOL;
echo strip_tags($text);

// actual output:
/*
 script Bad Javascript  script
Bad Javascript
*/

Using $ to represent subpatterns when using preg_replace()

<?php
$text = 'April 24, 2024 10:15 AM';
$pattern = '/^(\w+).*?(\d+).*?(\d{4})(.*?)$/';
$str = preg_replace($pattern, '$2 $1 $3$4', $text);
echo $str;
echo PHP_EOL;

// Actual output: "24 April 2024 10:15 AM"

PHP 5 to PHP 7 code converter using preg_replace_callback_array()

Example email validation regex from Andrey:

^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$

Example from Michael:

 $pattern = '/^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/';

Example from William:

$pattern = '/^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/';

Composer

Example of advanced usage including scripts

  • https://github.com/laminas/laminas-mvc-skeleton/blob/master/composer.json You can add alternates to packagist.org using the repositories key in the composer.json file
  • Example: https://wpackagist.org/ If you dependency issues, consider adding the --ignore-platform-reqs to the composer install or composer update directive
  • This is especially true if you're running 8.1 or 8.2 and the packagist project is set for PHP 7.4 or 8.0 If you want Composer to interactively build a composer.json file use this command:
composer --init

Web Services

SimpleXML Example:

<?php
// A simpleXML load file example
$xml = simplexml_load_file( 'produce.xml' );
 
// Get the vegies
$vegies = $xml->vegetables;
 
// Get the first vegie using array notation
$vegie = $vegies->vegetable[0]->name;
echo 'Content: ' . $vegie . "\n";

$fruits = $xml->fruits;
echo 'Content: ' . $fruits->fruit[0]->name . "\n" ;
echo 'Content: ' . $fruits->fruit[1]->name . "\n" ;
echo 'Content: ' . $fruits->fruit[2]->name . "\n" ;
 
// Output item data
foreach ( $fruits->fruit as $node ) {
    echo 'Content: ' . $node->name . "\n" ;
}
 
// Output XML from the SimpleXMLElement object
//echo $xml->asXML();
 
// Output to an xml file
$xml->asXML( 'newproduce.xml' );

// actual ouput (minus the XML document)

//var_dump($xml);

/*
Content: tomatoes
Content: strawberries
Content: bananas
Content: apples
Content: strawberries
Content: bananas
Content: apples

*/

Here's the XML document:

<?xml version="1.0" encoding="UTF-8"?>
<produce xmlns:ea="test">
	<vegetables>
		<vegetable unit="pound">
			<name>tomatoes</name>
			<price>2.99</price>
		</vegetable>
		<vegetable unit="bunch">
			<name>broccoli</name>
			<price>4.99</price>
		</vegetable>
	</vegetables>
	<fruits>
		<fruit unit="pint">
			<name>strawberries</name>
			<price>4.99</price>
			<time>seasonal</time>
		</fruit>
		<fruit unit="bunch">
			<name>bananas</name>
			<price>3.99</price>
			<time>seasonal</time>
		</fruit>
		<fruit unit="bag">
			<name>apples</name>
			<price>4.99</price>
			<time>seasonal</time>
		</fruit>
	</fruits>
</produce>

Example of SOAP Client

<?php
$data = array ('foo' => 'bar', 'bar' => 'baz');
$data = http_build_query($data);
$context_options = array (
        'http' => array (
            'method' => 'POST',
            'header'=> "Content-type: application/x-www-form-urlencoded\r\n"
                . "Content-Length: " . strlen($data) . "\r\n",
            'content' => $data
            )
        );

$context = stream_context_create($context_options)
$fp = fopen('https://url', 'r', false, $context);

Study by Oracle that compares SOAP and REST

Output Control

Example where you get a Warning "headers already sent"

<?php
error_reporting(E_ALL);
ini_set('display_errors', 1);

// stops buffering
ob_end_clean();

header('Test-1: TEST1');
echo '<br />' . __FILE__ . ':' . __LINE__;

// returns a Warning:
header('Test-2: TEST2');
echo '<br />' . __FILE__ . ':' . __LINE__;

// actual output:
/*
/home/vagrant/Zend/workspaces/DefaultWorkspace/sandbox/test.php:6
Warning: Cannot modify header information - headers already sent by (output started at /home/vagrant/Zend/workspaces/DefaultWorkspace/sandbox/test.php:6) in /home/vagrant/Zend/workspaces/DefaultWorkspace/sandbox/test.php on line 8

/home/vagrant/Zend/workspaces/DefaultWorkspace/sandbox/test.php:9
*/

Example using output buffering to create inner content

<?php
ob_start ();

$values = ['TH'=>'Thailand','GB'=>'Great Britain','FR'=>'France'];
foreach ($values as $key => $val)
    echo '<tr><th>' . $key . '</th><td>' . $val . '</td></tr>';

$contents = ob_get_clean();

echo '<h1>My Cool Webpage</h1>';
echo '<table>';
echo $contents;
echo '</table>';

Simplified ETag Example:

Web Services

REST request example:

Dependency Injection

Great overview of the DI design pattern:

Q & A

error_reporting=E_ALL
display_errors=on
  • Q: What are the typical settings for max-age in this header:
header('Cache-Control: must-revalidate, max-age=0');

<?php
class Test
{
    const FORMAT = 'l, d M Y';
    // this doesn't work:
    // public $time = new DateTime();
    // this DOES work:
    public function __construct(public DateTime $time = new DateTime()) {}
    public function getTime()
    {
        return $this->time->format(self::FORMAT);
    }
}
$test = new Test();
echo $test->getTime();

Q: Can you use filter_var() with the FILTER_VALIDATE_EMAIL flag in place of a regex? A: It works at a very basic level, but doesn't catch everything. Recommend to a regex for rigorous validation (see examples below)

Q: Do you have an example using preg_grep()? A: See: https://github.com/dbierer/classic_php_examples/blob/master/regex/preg_grep.php

Q: What is "skeleton loading?" A: Still researching this. From what I could see thus far, it appears to be a front-end technology.

Q: What some alternate reasons to use ob_start() A: One good reason is to have the ability to short-circuit long-running AJAX requests!

Q: What are other design patterns that have superceded MVC? A: There are plenty of modern alternatives.

Q: How do you set the (or find) the nesting limit for a particular PHP installation? A: There is no default nesting level for PHP -- it's determined by the OS. However, if you have XDebug installed, any errors might originate from that extension.

Q: Instructions for adding additional language input sources to change keyboard to German A: See: https://askubuntu.com/questions/1272094/how-to-install-a-german-keyboard-layout-on-an-english-installation

Q: Reference to readonly properties? A: Introduced in PHP 8.1. In PHP 8.2 support was added for readonly classes

<?php
// "backed" enum
// just by putting a return data type of `string` 
enum Gender : string
{
    case MALE = 'M';
    case FEMALE = 'F';
    case OTHER = 'O';
}

echo Gender::MALE->value;	// output: "M"

Change Request