Predefined Constants in PHP

•  __FILE__ The name of the script file being parsed. 
•  __LINE__ The number of the line in the script being parsed. 
•  PHP_VERSION The version of PHP in use. 
•  PHP_OS The operating system using PHP.

<?
echo "<br>This file is ".__FILE__;
echo "<br>This is line number ".__LINE__;
echo "<br>I am using ".PHP_VERSION;
echo "<br>This test is being run on ".PHP_OS;
?>