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

self:: keyword used for the current class and basically it is used to access static members, methods, and constants. But in case of $this you cannot call the static member, method and functions.

You can use the self:: keyword in another class and access the static members, method and constants. When it will be extends from parent class and same in case of $this keyword. You can access the non static members, method and function in another class when it will be extends from parent class.

The code given below is a example of self:: and $this keyword. Just copy and paste the code in your code file and see the output.

class cars{
    var $doors=4;   
    static $car_wheel=4;

  public function car_features(){
    echo $this->doors." Doors 
";
    echo self::$car_wheel." Wheels 
"; 
  }
}

class spec extends cars{
    function car_spec(){
        print(self::$car_wheel." Doors 
");
        print($this->doors." Wheels 
");
    }
}

/********Parent class output*********/

$car = new cars;
print_r($car->car_features());

echo "------------------------
";

/********Extend class from another class output**********/


$car_spec_show=new spec;

print($car_spec_show->car_spec());