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

Whenever you want to use a variable that is outside of the function but inside the same class, you use $this. It is a core php concept.

Answer 2

$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.

Answer 3

no i think ur idea is wrong.. $this is used when refers to a object of the same class.. like this

think we have a variable value $var and in THAT instance of that object should be set to 5

$this->var=5;

Answer 4

It's used in Object-oriented Programming (OOP):

<?php
class Example
{  
    public function foo()
    {
        //code
    }

    public function bar()
    {
        $this->foo();
    }
}

The pseudo-variable $this is available when a method is called from within an object context. $this is a reference to the calling object (usually the object to which the method belongs, but possibly another object, if the method is called statically from the context of a secondary object).

Answer 5

The most common use case is within Object Oriented Programming, while defining or working within a class. For example:

class Horse {
    var $running = false;

    function run() {
        $this->running = true;
    }
}

As you can see, within the run function, we can use the $this variable to refer to the instance of the Horse class that we are "in". So the other thing to keep in mind is that if you create 2 Horse classes, the $this variable inside of each one will refer to that specific instance of the Horse class, not to them both.

Answer 6

You would only use $this if you are doing Object Oriented programming in PHP. Meaning if you are creating classes. Here is an example:

class Item {
  protected $name, $price, $qty, $total;

  public function __construct($iName, $iPrice, $iQty) {
    $this->name = $iName;
    $this->price = $iPrice;
    $this->qty = $iQty;
    $this->calculate();
  }

}