PHP’s Magic Constants: __LINE__ , __FILE__, __FUNCTION__, __CLASS__, and __METHOD__
Setting constants in PHP is as easy as using the define function, but PHP creates a few constants in every script for you that help mostly for debugging purposes (well, that's generally the only time I use them). These constants are called "magic constants."
Magic constants have a funny syntax, placing two underscores before and after the constant's word representation. These are PHP's magic constants:
__LINE__
__FILE__
__FUNCTION__
__CLASS__
__METHOD__
You can imagine how helpful these constants are for debugging...but if you can't:
if($sugar == '') { echo('$sugar has no value on line '.__LINE__.' of ['.__FILE__.']'); }
There are also helpful uses for these magic constants:
dirname(__FILE__) // get the directory name of the current script
What do you use them for?
![Interview with a Pornhub Web Developer]()
Regardless of your stance on pornography, it would be impossible to deny the massive impact the adult website industry has had on pushing the web forward. From pushing the browser's video limits to pushing ads through WebSocket so ad blockers don't detect them, you have...
![7 Essential JavaScript Functions]()
I remember the early days of JavaScript where you needed a simple function for just about everything because the browser vendors implemented features differently, and not just edge features, basic features, like addEventListener and attachEvent. Times have changed but there are still a few functions each developer should...
![Create Snook-Style Navigation Using MooTools]()
Jonathan Snook debuted a great tutorial last September detailing how you can use an image and a few jQuery techniques to create a slick mouseover effect. I revisited his article and ported its two most impressive effects to MooTools.
The Images
These are the same...
![Facebook-Style Modal Box Using MooTools]()
In my oh-so-humble opinion, Facebook's Modal box is the best modal box around. It's lightweight, subtle, and very stylish. I've taken Facebook's imagery and CSS and combined it with MooTools' awesome functionality to duplicate the effect.
The Imagery
Facebook uses a funky sprite for their modal...
My two favorite are
That you can use it to get parent directory:
or you can include the init.php file from anywhere in your filesystem:
You would use
in the init.php
Wow, awesome usage of the __FILE__ magic constant — I hadn’t thought of that one!
Useful!
To Jesus DeLaTorre:
Maybe it could be better, when you use this:
$dir = str_replace ( “\”, “/”, dirname ( _FILE_ ) )
-> for Windows based systems
(PS: nice book engine)
thanks for this, i knew only __FILE__ so i googled this article :)
@jeezaa:
Instead of
/for linux and\for windows, just use another constant:omg @ the comments
realpath(dirname(__FILE__)) or
__DIR__ or
realpath(dirname(__FILE__).’/..’).’/file.bla’
is there any way to get the constants defined in a php file using
define()?
Yes there is. The function get_defined_constants() shows you all of the defined constants see: http://www.php.net/manual/en/function.get-defined-constants.php.
I have never seen the use of __FUNCTION__
Can give me any Example.
I make it a habit to wrap these magic constants into SQL and PL/SQL blocks so that I can quickly trace the construction of queries and DML to the source.
There’s also the
__NAMESPACE__constant, e.g.namespace hyperdrive; add_action('wp_head', __NAMESPACE__ .'\engage');