When to use self over $this?

Question

In PHP 5, what is the difference between using self and $this?

When is each appropriate?

Answer 1

Case 1: Use self can be used for class constants

 class classA { 
     const FIXED_NUMBER = 4; 
     self::POUNDS_TO_KILOGRAMS
}

If you want to call it outside of the class, use classA::POUNDS_TO_KILOGRAMS to access the constants

Case 2: For static properties

class classC {
     public function __construct() { 
     self::$_counter++; $this->num = self::$_counter;
   }
}