- str_replace: documentation ( source)
- realpath: documentation ( source)
<?php
$source = str_replace('\\', DIRECTORY_SEPARATOR, realpath($source)) . '<br>';
$docRoot = str_replace('/', '\\', $_SERVER['DOCUMENT_ROOT']). '<br>'; // normalize to http
$diff = str_replace($docRoot, '', $source). '<br>';
echo $source;
echo $docRoot;
echo $diff;
?>