minte9

LearnRemember

Instantiation

A class is only a blueprint, it must be instantiated into object before use. For instantiation use new constructor keyword.

 
class myClass 
{ 
    // Class contents go here
}

$myClassInstance = new myClass();

Reference

An object is always passed by reference (different from others type of variables). For Object & are not needed.

 
class A 
{
    public $foo = 1;
}  

$a = new A;    
$b = $a; // both $a and $b will point to the same object

echo $a->foo; // 1

$a->foo = 2;

echo $b->foo; // 2 - Look Here

Reinstantiation

Object reinstantiation breaks the reference.

 
class myClass 
{
    public $foo;
    public function __construct($val) 
    {
        $this->foo = $val;
    }
}

$a = new myClass(1);
$b = $a;

echo $a->foo; // 1

$a->foo = 2;
echo $b->foo; // 2

$a = new myClass(2); // Look Here

echo $a->foo; // 2
echo $b->foo; // 1 -> reference is broken

Inheritance

Class Inheritance allows a class to extend another class. Parent classes can be accessed using the special parent:: namespace.

 
class A 
{
    function test() 
    {
        echo "A";
    }
}

class B extends A 
{
    function test() 
    {
        parent::test(); // A
        echo "B";
    }
}

$a = new A();
$b = new B();

$a->test(); // A
$b->test(); // AB