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Constants and Magic Constants in PHP   Share / Like
Constants are named values whose values cannot be changed. When you create a constant you should use all capital letters and underscores separating words to let yourself and others know they are constants. A dollar sign is not needed in front of the name when creating constants. We use the define() function in PHP to create them.

Here is how we create a constant, and use true on the end to make it not worry about letter casing:
Learn HTML
<?php

// define(constant_name, value, case_sensitive=true);
define("AUTHOR_NAME""Adam Khoury"true);

echo 
"The person that created this web page is named " AUTHOR_NAME ".";

?>

Develop PHP browser display window
The person that created this web page is named Adam Khoury.




Magic Constants (predefined)

PHP also has predefined magic constants available for you to use. Here we demonstrate a few:

Learn HTML
<?php
// __LINE__ Returns the current line number of the file.  
echo __LINE__;
echo 
"<br />";
// __FILE__  Returns the full path and filename of the file. If used inside an include, the name of the included file is returned. 
echo __FILE__;
echo 
"<br />";
// __FUNCTION__  Returns the function name the code is currently executing inside of
echo __FUNCTION__;
echo 
"<br />";
// __CLASS__ The class name. As of PHP 5 this magic constant returns the class name as it was declared.
echo __CLASS__;
echo 
"<br />";
?>




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