What does the variable $this mean in PHP?

Php Problem Overview

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 variable $this works in PHP?

Php Solutions

Solution 1 - Php

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

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.

Solution 2 - Php

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

Solution 3 - Php

I know its old question, anyway another exact explanation about $this. $this is mainly used to refer properties of a class.

Example:

Class A
{
   public $myname;    //this is a member variable of this class

function callme() {
    $myname = 'function variable';
    $this->myname = 'Member variable';
    echo $myname;                  //prints function variable
    echo $this->myname;              //prints member variable
   }
}

output:

function variable

member variable

Solution 4 - Php

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).

Solution 5 - Php

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'

Solution 6 - Php

when you create a class you have (in many cases) instance variables and methods (aka. functions). $this accesses those instance variables so that your functions can take those variables and do what they need to do whatever you want with them.

another version of meder's example:

class Person {

	protected $name;  //can't be accessed from outside the class

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

	public function getName() {
		return $this->name;
	}
}
// this line creates an instance of the class Person setting "Jack" as $name.  
// __construct() gets executed when you declare it within the class.
$jack = new Person("Jack"); 

echo $jack->getName();

Output:

Jack

Solution 7 - Php

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

Solution 8 - Php

$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).

Solution 9 - Php

$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/>";
  }
}
?>

Solution 10 - Php

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

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

Solution 11 - Php

Generally, this keyword is used inside a class, generally with in the member functions to access non-static members of a class(variables or functions) for the current object.

this keyword should be preceded with a $ symbol.
In case of this operator, we use the -> symbol.
Whereas, $this will refer the member variables and function for a particular instance.

Let's take an example to understand the usage of $this.

<?php
class Hero {
    // first name of hero
    private $name;
    
    // public function to set value for name (setter method)
    public function setName($name) {
        $this->name = $name;
    }
    
    // public function to get value of name (getter method)
    public function getName() {
        return $this->name;
    }
}

// creating class object
$stark = new Hero();

// calling the public function to set fname
$stark->setName("IRON MAN");

// getting the value of the name variable
echo "I Am " . $stark->getName();
?>

> OUTPUT: I am IRON MAN

NOTE: A static variable acts as a global variable and is shared among all the objects of the class. A non-static variables are specific to instance object in which they are created.

Content Type	Original Author	Original Content on Stackoverflow
Question	waiwai933	View Question on Stackoverflow
Solution 1 - Php	meder omuraliev	View Answer on Stackoverflow
Solution 2 - Php	Eric Leschinski	View Answer on Stackoverflow
Solution 3 - Php	loyola	View Answer on Stackoverflow
Solution 4 - Php	snicker	View Answer on Stackoverflow
Solution 5 - Php	user6485832	View Answer on Stackoverflow
Solution 6 - Php	cp3	View Answer on Stackoverflow
Solution 7 - Php	Keikai	View Answer on Stackoverflow
Solution 8 - Php	Neg	View Answer on Stackoverflow
Solution 9 - Php	homi	View Answer on Stackoverflow
Solution 10 - Php	Marc W	View Answer on Stackoverflow
Solution 11 - Php	Praveen Neelanathan	View Answer on Stackoverflow

What does the variable $this mean in PHP?

Php Problem Overview

Php Solutions

Solution 1 - Php

Solution 2 - Php

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

Solution 3 - Php

Solution 4 - Php

Solution 5 - Php

Solution 6 - Php

Solution 7 - Php

Solution 8 - Php

Solution 9 - Php

Solution 10 - Php

Solution 11 - Php

Fast permutation -> number -> permutation mapping algorithms

Calculate the number of business days between two dates?

Attributions

Php Problem Overview

Php Solutions

Solution 1 - Php

Solution 2 - Php

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

Solution 3 - Php

Solution 4 - Php

Solution 5 - Php

Solution 6 - Php

Solution 7 - Php

Solution 8 - Php

Solution 9 - Php

Solution 10 - Php

Solution 11 - Php

Fast permutation -> number -> permutation mapping algorithms

Calculate the number of business days between two dates?

Attributions

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