can someone explain what this php code is doing or its purpose
<p>here is the snippit</p>

<pre><code>$thisFile = str_replace('\\', '/', __FILE__);
$docRoot = $_SERVER['DOCUMENT_ROOT'];

$webRoot  = str_replace(array($docRoot, 'library/config.php'), '', $thisFile);
$srvRoot  = str_replace('library/config.php', '', $thisFile);
</code></pre>

<p>if i save this into test.php as a file. the section that im getting confused on is how the str_replace is makeing the $webRoot value come out to test.php</p>
