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

It refers to the instance of the current class, as meder said.

See the PHP Docs. It's explained under the first example.

Answer 2

It's a reference to the current object, it's most commonly used in object oriented code.

• Reference: http://www.php.net/manual/en/language.oop5.basic.php
• Primer: http://www.phpro.org/tutorials/Object-Oriented-Programming-with-PHP.html

Example:

<?php
class Person {
    public $name;

    function __construct( $name ) {
        $this->name = $name;
    }
};

$jack = new Person('Jack');
echo $jack->name;

This stores the 'Jack' string as a property of the object created.

Answer 3

It is the way to reference an instance of a class from within itself, the same as many other object oriented languages.

From the PHP docs:

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 4

Lets see what happens if we won't use $this and try to have instance variables and constructor arguments with the same name with the following code snippet

<?php

class Student {
    public $name;

    function __construct( $name ) {
        $name = $name;
    }
};

$tom = new Student('Tom');
echo $tom->name;

?>

It echos nothing but

<?php

class Student {
    public $name;

    function __construct( $name ) {
        $this->name = $name; // Using 'this' to access the student's name
    }
};

$tom = new Student('Tom');
echo $tom->name;

?>

this echoes 'Tom'

Answer 5

This is long detailed explanation. I hope this will help the beginners. I will make it very simple.

First, let's create a class

<?php 

class Class1
{
    
}

You can omit the php closing tag ?> if you are using php code only.

Now let's add properties and a method inside Class1.

<?php 

class Class1
{
    public $property1 = "I am property 1";
    public $property2 = "I am property 2";

    public function Method1()
    {
        return "I am Method 1";
    }
}

The property is just a simple variable , but we give it the name property cuz its inside a class.

The method is just a simple function , but we say method cuz its also inside a class.

The public keyword mean that the method or a property can be accessed anywhere in the script.

Now, how we can use the properties and the method inside Class1 ?

The answer is creating an instance or an object, think of an object as a copy of the class.

<?php 

class Class1
{
    public $property1 = "I am property 1";
    public $property2 = "I am property 2";

    public function Method1()
    {
        return "I am Method 1";
    }
}

$object1 = new Class1;
var_dump($object1);

We created an object, which is $object1 , which is a copy of Class1 with all its contents. And we dumped all the contents of $object1 using var_dump() .

This will give you

object(Class1)#1 (2) { ["property1"]=> string(15) "I am property 1" ["property2"]=> string(15) "I am property 2" }

So all the contents of Class1 are in $object1 , except Method1 , i don't know why methods doesn't show while dumping objects.

Now what if we want to access $property1 only. Its simple , we do var_dump($object1->property1); , we just added ->property1 , we pointed to it.

we can also access Method1() , we do var_dump($object1->Method1());.

Now suppose i want to access $property1 from inside Method1() , i will do this

<?php 

class Class1
{
    public $property1 = "I am property 1";
    public $property2 = "I am property 2";

    public function Method1()
    {   
        $object2 = new Class1;
        return $object2->property1;
    }
}

$object1 = new Class1;
var_dump($object1->Method1()); 

we created $object2 = new Class1; which is a new copy of Class1 or we can say an instance. Then we pointed to property1 from $object2

return $object2->property1;

This will print string(15) "I am property 1" in the browser.

Now instead of doing this inside Method1()

$object2 = new Class1;
return $object2->property1;

We do this

return $this->property1;

The $this object is used inside the class to refer to the class itself.

It is an alternative for creating new object and then returning it like this

$object2 = new Class1;
return $object2->property1;

Another example

<?php 

class Class1
{
    public $property1 = 119;
    public $property2 = 666;
    public $result;

    public function Method1()
    {   
        $this->result = $this->property1 + $this->property2;
        return $this->result;
    }
}

$object1 = new Class1;
var_dump($object1->Method1());

We created 2 properties containing integers and then we added them and put the result in $this->result.

Do not forget that

$this->property1 = $property1 = 119

they have that same value .. etc

I hope that explains the idea.

This series of videos will help you a lot in OOP

https://www.youtube.com/playlist?list=PLe30vg_FG4OSEHH6bRF8FrA7wmoAMUZLv

Answer 6

$this is a special variable and it refers to the same object ie. itself.

it actually refer instance of current class

here is an example which will clear the above statement

<?php
 class Books {
  /* Member variables */
  var $price;
  var $title;

  /* Member functions */
  function setPrice($par){
     $this->price = $par;
  }

  function getPrice(){
     echo $this->price ."<br/>";
  }

  function setTitle($par){
     $this->title = $par;
  }

  function getTitle(){
     echo $this->title ." <br/>";
  }
}
?>