Basics

PHP Magic Constants

PHP magic constants like __LINE__ provide runtime context.

What Are PHP Magic Constants?

PHP magic constants are predefined constants that change based on where they are used. Unlike regular constants, magic constants are resolved at runtime, providing useful information about the script's execution environment. These constants are especially helpful for debugging, logging, and enhancing the clarity of your code.

List of PHP Magic Constants

__LINE__: The current line number of the file.
__FILE__: The full path and filename of the file.
__DIR__: The directory of the file.
__FUNCTION__: The function name (added in PHP 4.3.0).
__CLASS__: The class name (added in PHP 4.3.0).
__TRAIT__: The trait name (added in PHP 5.4.0).
__METHOD__: The class method name (added in PHP 5.0.0).
__NAMESPACE__: The current namespace (added in PHP 5.3.0).

Using LINE and FILE

The __LINE__ and __FILE__ constants are commonly used for debugging purposes. They can provide insight into where specific operations occur in your code, making it easier to track down issues.

Exploring DIR

The __DIR__ constant returns the directory of the file in which it's used. It's particularly useful for including files or dealing with file paths relative to the current script's location.

Understanding FUNCTION and METHOD

The __FUNCTION__ and __METHOD__ constants provide the name of the current function or class method, respectively. These can be very useful for error handling and logging.

Working with CLASS, TRAIT, and NAMESPACE

The __CLASS__, __TRAIT__, and __NAMESPACE__ constants provide information about the class, trait, and namespace contexts. This can be particularly helpful in large codebases where understanding the context of execution is crucial.

Basics

Previous: Constants
Next: Callback Functions

PHP Magic Constants