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Reflection was introduced in PHP 5 to inspect and to retrieve information and reverse-engineer classes, interfaces, functions and methods as well as extensions during runtime.

Snippets:

How to create an instance of a class using reflection in PHP:

// this code does the same as: $instance = new ClassName();
$class = new ReflectionClass("ClassName");
if ($class->isInstantiable())
	$instance = $class->newInstance();

Class Example

class Triangle{
	// a public member can be used from any point of the application:
	public $publicMember;

	// a protected member can be accessed only from within this class or from its subclasses:
	public $protectedMember;

	// a protected member can be accessed only from within this class:
	private $privateMember;

	// the constructor is a method(function) which does not return a parameter
	// and is invoked when the object is created:
	public function __construct($parameter)
	{
		echo "Constructor is invoked
";
	}
}

Interfaces - an interface defines a set of methods. Each class that implement and interface has to implement the methods defined in the interface.

A class can implement more than one interfaces.

interface Shape
{
	public function calculateArea();
}

class Triangle implements Shape{
	// because now Triangle implements shape, it has to implement the calculateArea function:
	public function calculateArea()
	{
		return 1000; // for the moment it returns a hardcoded value;
	}
}

Invoke parent constructor

class Car
{
    public function __construct($color)
    {
        parent::__construct($color);
        print "Creating a car\n";
    }

    public function accelerate() {
        print "Vroom!";
    }
}

class Toyota extends Car
{
    public function __construct($color) {
        parent::__construct($color);
        print "Creating a Toyota  Car\n";
    }

    public function accelerate() {
        print "Vroom Vroom!";
    }
}