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:
<?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 . ".";
?>
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:
<?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 />";
?>
