What does the variable $this mean in PHP?

Question

I see the variable $this in PHP all the time and I have no idea what it\'s used for. I\'ve never personally used it.

Can someone tell me how the variab

Answer 1

The best way to learn about the $this variable in PHP is to try it against the interpreter in various contexts:

print isset($this);              //true,   $this exists
print gettype($this);            //Object, $this is an object 
print is_array($this);           //false,  $this isn't an array
print get_object_vars($this);    //true,   $this's variables are an array
print is_object($this);          //true,   $this is still an object
print get_class($this);          //YourProject\YourFile\YourClass
print get_parent_class($this);   //YourBundle\YourStuff\YourParentClass
print gettype($this->container); //object
print_r($this);                  //delicious data dump of $this
print $this->yourvariable        //access $this variable with ->

So the $this pseudo-variable has the Current Object's method's and properties. Such a thing is useful because it lets you access all member variables and member methods inside the class. For example:

Class Dog{
    public $my_member_variable;                             //member variable

    function normal_method_inside_Dog() {                   //member method

        //Assign data to member variable from inside the member method
        $this->my_member_variable = "whatever";

        //Get data from member variable from inside the member method.
        print $this->my_member_variable;
    }
}

$this is reference to a PHP Object that was created by the interpreter for you, that contains an array of variables.

If you call $this inside a normal method in a normal class, $this returns the Object (the class) to which that method belongs.

It's possible for $this to be undefined if the context has no parent Object.

php.net has a big page talking about PHP object oriented programming and how $this behaves depending on context. https://www.php.net/manual/en/language.oop5.basic.php