What does the variable $this mean in 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

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.

1. this keyword should be preceded with a $ symbol.
2. In case of this operator, we use the -> symbol.
3. 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.