PHP Static Methods and Properties

There are two types of class members in PHP.

• Static Members
• Instance Members

The main differences are :

Syntax :- The static keyword is used to declare static methods and properties..

<?php
class MyClass {
  public static $staticVariable;
  public static function staticMethod() {
    echo "Hello World!";
  }
}
?>

Syntax :- Accessing a static methods and properties:

//  For Static Property
ClassName::staticPropertyName;
//  For Static Method
ClassName::staticMethodName();

Example 1 :- The following example contains a static property and method.

<?php
class MyClass {
  //    A static property
  public static $name = "ABC";
  //    A static method
  public static function sayHello() {
    echo "Hello";
  }
}
//  Call static property
echo MyClass::$name;
echo "<br />";
//  Call static method
MyClass::sayHello();
?>

Output :-

Example 2 :- The following example display difference between static members and instance members.

<?php
class MyClass {
  //    A static property
  public static $x = 10;
  //    A instance property
  public $y = 10;
  function showXY()
  {
	echo "X = " . MyClass::$x . " , Y = " . $this->y . "<br />";
	MyClass::$x += 1;
	$this->y += 1;
  }
}
$obj1 = new MyClass();
$obj2 = new MyClass();
$obj3 = new MyClass();
$obj1->showXY();
$obj2->showXY();
$obj3->showXY();
$total = MyClass::$x + $obj1->y + $obj2->y + $obj3->y;
echo "<br /><br />The total is : " . $total;
?>

Output :-

Note:- Static and non-static methods are both possible in a same class.

Use the self keyword followed by a double colon (::) to access a static method from a method in the same class.