Why do we have to use $this-> operator? | PHP

Question

I'm developing an application in PHP. I am trying to figure out the use of $this-> and why it is always preferred.

I mean we can simply echo a property value inside a method using this code

<?php
class place{
    public $country;
    public function countryName($country){
        echo $country;
    }
}
$info = new place();
$info->countryName("Nepal");
?>

But, in examples I see that $this-> is used in this way:

<?php
class place{
    public $country;
    public function countryName($country){
        $this->country = $country;
        echo $this->country;
    }
}
$info = new place();
$info->countryName("Nepal");
?>

Is the use of $this-> preferred or is the first method totally normal?

the first method is not echoing any properties... you cannot compare the two codes. — Karoly Horvath, Nov 14 '14 at 17:30
@JayBlanchard, PHP handles `this` differently than other languages such as Java and C#. http://stackoverflow.com/questions/4353970/this-keyword-in-java-and-in-php — Daryl Bennett, Nov 14 '14 at 17:41
True @DarylBennett, but the concept of `this` is persistent throughout OOP. — Jay Blanchard, Nov 14 '14 at 17:42

score 5 · Accepted Answer · answered Nov 14 '14 at 17:30

$this is referencing to the current object.

As per php.net

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).

score 4 · Answer 2 · answered Nov 14 '14 at 17:36

4

$this->country

is country relative to the class

$country

is relative to the method

answered Nov 14 '14 at 17:36

Taku

5,639
2
42
31

score 2 · Answer 3 · answered Nov 14 '14 at 17:28

$this->country will echo out your class level $country whereas just echo $country will echo out your method level $country. This is all because of how objects work in PHP and the scope of variables. As you keep looking you'll see the use of this a lot more

score 2 · Answer 4 · answered Nov 14 '14 at 17:28

The first arc isn't echoing a property it's just echoing the value that is passed in.

The second arc assigns the passed in value to the property, and then you use $this->country to echo the property.

If you echo $this->country in the first arc, you'll get nothing echo'd.

Daryl Bennett · Answer 5 · 2014-11-14T17:40:28.683

2

$this->

Helps you refer to your class variables.

for example:

   public function countryName($country){
         $this->country = $country;
        echo $this->country;
    }

Your $this->country is referring to the class var, and it's needed to be set to the parameter $country.

edited Nov 14 '14 at 17:40

answered Nov 14 '14 at 17:30

Daryl Bennett

462
10
22

Pardon me, it would appear that I'm mistaken. You can code without it in Java and other OOP, but it looks like in PHP you need to use `$this` http://stackoverflow.com/questions/4353970/this-keyword-in-java-and-in-php – Daryl Bennett Nov 14 '14 at 17:38

onlyforthis · Answer 6 · 2014-11-15T08:17:38.627

$this represents any instance of the class. So when you create an object $USA and call countryName($country), $this will represent the object $USA:

<?php
$USA = new place();
$USA->countryName("USA");
?>

In your code, you are echoing the parameter of the function countryName($country) but not the class attribute, but here:

<?php
class place{
    public $country;//This is the class attribute.
    public function countryName($country){
        $this->country = $country;/*here you are storing the value of the parameter passed to the function into the class attribute ($this->country)*/
        echo $this->country;
    }
}
?>

score 1 · Answer 7 · answered May 15 '19 at 23:26

The advantage to using $this->country versus $country, is that you can use $this->country in other places as well. The value is stored in the object $info.

For example:

// #1 case
class place {
  public $country; // This is not used
  public function countryName($country) {
    echo $country;
  }
}

$info = new place();
$info->countryName("Nepal");
// Result:
//   Nepal


// #2 case: Using $this
class place {
  public $country; // This is not used
  public function countryName($country) {
    $this->country = $country;
    echo $this->country;
  }
  public function whereAmI() { // NO parameters
    echo 'You are in the country "' . $this->country . '"';
  }
}

$info = new place();
$info->countryName("Nepal");
$info->whereAmI();
// Result:
//   Nepal
//   You are in the country "Nepal"

Why do we have to use $this-> operator? | PHP

7 Answers7