Get to know 9 Magic Constants in PHP that you may often use

PHP has many constants that are ready to use (predefined) , without having to be created.

A constant is a value that will never change and cannot be changed.

However, there are 9 magic constants in PHP that will always change in value depending on their use.

What are they?

Let's discuss ...

1. Constants __LINE__

This constant will contain a value that states the current line number.

Example:

<?php
echo "Ini beris pertama<br>";
echo "Ini baris ke: " . __LINE__."<br>";
echo "ini baruus ketiga<br>";
?>

The result:

Why are the results 3?

Because the location of constants __LINE__is in the 3rd row. We can see this with the text editor.

2. Constants __FILE__

This constant will contain the full address (path) of the PHP file.

Example:

<?php
echo "File ini berada di: " . __FILE__;
?>

The result:

3. Constants __DIR__

Similar to constants __FILE__, constants __DIR__will contain directory addresses from PHP files.

Example:

<?php
echo "File ini berada di direktori: " . __DIR__;
?>

The result:

The constellation is __DIR__usually used to import other files like this:

<?php include __DIR__."/config.php"; ?>

4. Constants __FUNCTION__

This constant will contain the name of the function.

Example:

<?php
function aku_lapar() {
    echo "Nama fungsi ini adalah: " . __FUNCTION__;
}

// panggil fungsi
aku_lapar();
?>

The result:

5. Constants __CLASS__

The constant __CLASS__will contain the name of the class .

Example:

<?php
class ManusiaSerigala {

    function printClassName(){
        echo "Nama class adalah: ".__CLASS__;
    }
}

// membuat objek
$aku = new ManusiaSerigala();
$aku->printClassName();
?>

The result:

6. Constants __TRAIT__

The constant __TRAIT__will contain the name of the trait and namespace .

Example:

<?php
// membuat namespace
namespace Enemy;

// membuat trait
trait Makhluk {
    function printTrait() {
        echo "Nama Trait adalah: ".__TRAIT__;
    }
}

class ManusiaSerigala {

    use Makhluk;

}

// membuat objek
$aku = new ManusiaSerigala();
$aku->printTrait();
?>

The result:

7. Constants __METHOD__

Constants are the __METHOD__same as constants __FUNCTION__. It will contain the name of the method and class where it is used.

Example:

<?php
class ManusiaSerigala {

    function lari(){
        echo "ini adalah method: ".__METHOD__."<br>";
    }

    function lompat(){
        echo "ini adalah method: ".__METHOD__."<br>";
    }
}

// membuat objek
$aku = new ManusiaSerigala();
$aku->lari();
$aku->lompat();
?>

The result:

8. Constants __NAMESPACE__

The constant __NAMESPACE__will contain the namespace name .

Example:

<?php
// membuat namespace
namespace Enemy;

class ManusiaSerigala {

    function printNamaNamespace(){
        echo "Nama namespace adalah: ".__NAMESPACE__;
    }
}

// membuat objek
$aku = new ManusiaSerigala();
$aku->printNamaNamespace();
?>

The result:

9. Constants ClassName::class

Almost like __TRAIT__, a constant ClassName::classwill contain the name of the class and namespace .

Example:

<?php
namespace Makhluk {
    class ManusiaSerigala {
    }
    
    echo "Nama class adalah: ".ManusiaSerigala::class;
}
?>

The result:

Reference: https://www.petanikode.com/php-magic-constant