When would you use the $this keyword in PHP?

Question

When would you use the $this keyword in PHP? From what I understand $this refers to the object created without knowing the objects name.

Al

Answer 1

$this is used when you have created a new instance of an object.

For example, imagine this :

class Test {
    private $_hello = "hello";

    public function getHello () {
        echo $this->_hello; // note that I removed the $ from _hello !
    }

    public function setHello ($hello) {
        $this->_hello = $hello;
    }
}

In order to access to the method getHello, I have to create a new instance of the class Test, like this :

$obj = new Test ();
// Then, I can access to the getHello method :
echo $obj->getHello ();
// will output "hello"

$obj->setHello("lala");
echo $obj->getHello ();
// will output "lala"    

In fact, $this is used inside the class, when instancied. It is refered as a scope.

Inside your class you use $this (for accessing *$_hello* for example) but outside the class, $this does NOT refer to the elements inside your class (like *$_hello*), it's $obj that does.

Now, the main difference between $obj and $this is since $obj access your class from the outside, some restrictions happens : if you define something private or protected in your class, like my variable *$_hello*, $obj CAN'T access it (it's private!) but $this can, becase $this leave inside the class.