PHP self:: vs static::

self:: – Early Binding

Resolves to the class where the method is defined. Overrides in child classes do not affect it.

Example – Methods:

class A {
	public static function who() { echo "A"; }
	public static function test() { self::who(); }
}

class B extends A {
	public static function who() { echo "B"; }
}

B::test(); //Output: A

Example – Properties:

class A {
	protected static $value = 'A';
	public static function get() { return self::$value; }
}

class B extends A {
	protected static $value = 'B';
}

echo B::get(); //Output: A

static:: – Late Static Binding (LSB)

Resolves to the class that made the call, respecting inheritance. Allows polymorphic behavior.

Example – Methods:

class A {
	public static function who() { echo "A"; }
	public static function test() { static::who(); }
}

class B extends A {
	public static function who() { echo "B"; }
}

B::test(); //Output: B

Example – Properties:

class A {
	protected static $value = 'A';
	public static function get() { return static::$value; }
}

class B extends A {
	protected static $value = 'B';
}

echo B::get(); //Output: B

Key Differences

Rule of Thumb

• Use self:: when behavior should never change in child classes.
• Use static:: for polymorphic behavior (factories, ActiveRecord, extensible classes).