If you are trying to find a file on your include path, there is a better way: http://php.net/manual/en/function.stream-resolve-include-path.php
(PHP 4 >= 4.3.0, PHP 5, PHP 7)
get_include_path — Gets the current include_path configuration option
Gets the current include_path configuration option value.
Returns the path, as a string.
Example #1 get_include_path() example
<?php
// Works as of PHP 4.3.0
echo get_include_path();
// Works in all PHP versions
echo ini_get('include_path');
?>
If you are trying to find a file on your include path, there is a better way: http://php.net/manual/en/function.stream-resolve-include-path.php