Where's the difference between self and $this-> in a PHP class or PHP method?

$this refers to the instance of the class, that is correct. However, there is also something called static state, which is the same for all instances of that class. self:: is the accessor for those attributes and functions.

Also, you cannot normally access an instance member from a static method. Meaning, you cannot do

static function something($x) {
  $this->that = $x;
}

because the static method would not know which instance you are referring to.

$this refers to the current object, self refers to the current class. The class is the blueprint of the object. So you define a class, but you construct objects.

So in other words, use self for static and this for non-static members or methods.

1. this-> can't access static method or static attribute , we use self to access them.

2. $this-> when dealing with extended class will refer to the current scope that u extended , self will always refer to the parent class because its doesn't need instance to access class method or attr its access the class directly.

   <?php
   class FirstClass{
     function selfTest(){
       $this->classCheck();
       self::classCheck();
     } 
     function classCheck(){
       echo "First Class";
     }
   }
   class SecondClass extends FirstClass{
       function classCheck(){
         echo "Second Class";
       }
   }
   $var = new SecondClass();
   $var->selfTest(); //this-> will refer to Second Class , where self refer to the parent class