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

Inside a class definition, $this refers to the current object, while self refers to the current class.

It is necessary to refer to a class element using self, and refer to an object element using $this.

self::STAT // refer to a constant value
self::$stat // static variable
$this->stat // refer to an object variable