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

• The object pointer $this to refers to the current object.
• The class value static refers to the current object.
• The class value self refers to the exact class it was defined in.
• The class value parent refers to the parent of the exact class it was defined in.

See the following example which shows overloading.

newThisClass()); // B
var_dump($b->newParentClass()); // A


class C extends B
{
    public static function newSelfClass()
    {
        return new self;
    }
}


$c = new C;

var_dump($c::newStaticClass()); // C
var_dump($c::newSelfClass()); // C because self now points to "C" class
var_dump($c->newThisClass()); // C
var_dump($b->newParentClass()); // A because parent was defined *way back* in class "B"

Most of the time you want to refer to the current class which is why you use static or $this. However, there are times when you need self because you want the original class regardless of what extends it. (Very, Very seldom)