When will you use this $ keyword in PHP?

Question

When do you use the $this in PHP? From what I understand, $this refers to an object created without knowing the name of the object.

Also, the keyword $this can only be used in a method?

Will give an example when you can use $this .

Answer 1

A class can contain its own constants, variables (called "properties") and functions (called "methods").

 <?php class SimpleClass { // property declaration public $var = 'a default value'; // method declaration public function displayVar() { echo $this->var; } } ?> 

Some examples of the $ this pseudo-variable:

 <?php class A { function foo() { if (isset($this)) { echo '$this is defined ('; echo get_class($this); echo ")\n"; } else { echo "\$this is not defined.\n"; } } } class B { function bar() { // Note: the next line will issue a warning if E_STRICT is enabled. A::foo(); } } $a = new A(); $a->foo(); // Note: the next line will issue a warning if E_STRICT is enabled. A::foo(); $b = new B(); $b->bar(); // Note: the next line will issue a warning if E_STRICT is enabled. B::bar(); ?> 

The above example outputs:

• $ this is defined (A)
• $ this is undefined.
• $ this is defined (B)
• $ this is undefined.

Answer 2

The most common use case is in object-oriented programming, defining or working inside a class. For example:

 class Horse { var $running = false; function run() { $this->running = true; } } 

As you can see, in the run function we can use the $this variable to refer to the instance of the Horse class that we are in. Therefore, it should be borne in mind that if you create 2 classes of horses, the $this variable inside each will refer to this particular instance of the Horse class, and not to both of them.

Answer 3

You would only use $ this if you are doing object oriented programming in PHP. Value if you create 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(); } } 

Answer 4

$ is used to create a link to the current instance of the object. This way you can do things like:

 class MyClass { private $name; public function setName($name) { $this->name = $name; } //vs public function setName($pName) { $name = $pName; } } 

It is also useful to use the following methods:

 class MyClass2 { private $firstName; private $lastName; public function setFirstName($name) { $this->firstName = $name; return $this; } public function setLastName($name) { $this->lastName = $name; return $this; } public function sayHello() { print "Hello {$this->firstName} {$this->lastName}"; } } //And now you can do: $newInstance = new MyClass2; $newInstance->setFirstName("John")->setLastName("Doe")->sayHello(); 

Answer 5

It is 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 the method is called from within the object context. $ 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 the secondary object).

Answer 6

Once I know that the ultimate use of the this equivalent in other languages ​​is to implement the Free interface; each class method that would otherwise return void instead returns this , so method calls can be easily chained together.

 public function DoThis(){ //Do stuff here... return $this; } public function DoThat(){ //do other stuff here... return $this; } 

The above could be called so:

 myObject->DoThis()->DoThat(); 

Which may be useful for some things.

Answer 7

Used when you want to work with local variables.

You can also read about it from here .

 function bark() { print "{$this->Name} says Woof!\n"; } 

Answer 8

$ this is used when you create a new instance of the 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; } } 

To access the getHello method, I have to create a new instance of the Test class, for example:

 $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 this is not possible. This is called an area .

Inside your class, you use $ this (to access * $ _ hello *, for example), but outside the class, $ this does NOT apply to elements inside your class (e.g. * $ _ hello *), this is what $ obj does.

Now the main difference between $ obj and $ is that $ obj gets access to your class from outside , some restrictions occur: if you define something private or protected in your class, for example, my variable * $ _ hello *, $ obj CANNOT access it (it's private!), but $ this can becase $ this to leave inside the class.

Answer 9

No, I think ur idea is wrong .. $this used when referring to an object of the same class .. like this

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

$ this-> variable = 5;

Answer 10

Using $ this refers to reference methods or instance variables belonging to the current object

$ this-> name = $ name or $ This-> callSomeMethod ()

which will use a variable or method implemented in the current object by a subclass or not.

If you want to specifically call the implementation of the parent class, you would do something like

Parent :: callSomeMethod ()

Answer 11

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

Answer 12

 <?php class identity { public $name; public $age; public function display() { return $this->name . 'is'. $this->age . 'years old'; } } ?>