PHP Tutorial

PHP MAGIC CONSTANTS

🪄 PHP Magic Constants

Magic constants in PHP are predefined constants that change depending on where they are used. These are extremely useful for debugging, file handling, and code tracking.

Note: Magic constants start and end with double underscores __.

📋 List of PHP Magic Constants

Constant	Description
`__LINE__`	Returns the current line number in the file.
`__FILE__`	Returns the full path and filename of the file.
`__DIR__`	Returns the directory of the file.
`__FUNCTION__`	Returns the name of the current function.
`__CLASS__`	Returns the name of the current class.
`__METHOD__`	Returns the name of the current class method.
`__NAMESPACE__`	Returns the current namespace name.
`__TRAIT__`	Returns the name of the current trait.

🔍 Commonly Used Magic Constants

<?php
echo "This is line number: " . __LINE__;
echo "<br>This file is: " . __FILE__;
echo "<br>This directory is: " . __DIR__;
?>

🧠 Inside a Function

<?php
function test() {
  echo "Function name: " . __FUNCTION__;
}
test();
?>

🏛️ Inside a Class

<?php
class Demo {
  public function showInfo() {
    echo "Class name: " . __CLASS__;
    echo "<br>Method name: " . __METHOD__;
  }
}

$obj = new Demo();
$obj->showInfo();
?>

Tip: Magic constants are super helpful when debugging or building logging systems.

🚫 You Cannot Redefine Them

Since magic constants are built-in and dynamic, you cannot override them using define() or any other method.

📌 Summary

Start and end with __.
Provide metadata like file path, class, method, etc.
Change value depending on context of use.
Common in debugging, logging, and dynamic apps.

Want more? Try using these constants inside included files and see how they behave differently!

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