find caller script path from a library
<p>When execution a script that includes a library, I whant to find from whithin the library the caller script, in Perl I'm using env: <code>$0</code> that gives me the path to the caller script. In PHP <code>__FILE__</code> gives me the current script, so in the library it gives me the library path not the caller script path.</p>

<p>from perl documentation: <strong>$0 Contains the name of the file containing the Perl script being executed.</strong> </p>

<p>I think It can be done using debug_backtrace(), but there is another better/shorter method ?</p>

<p><strong>EDIT:</strong>   (added sample code)  </p>

<p>file: index.php</p>

<pre><code>&lt;?php
require 'locallib.php';
echo 'in original script = '.__FILE__.'&lt;br /&gt;';
?&gt;
</code></pre>

<p>file: locallib.php</p>

<pre><code>&lt;?php
require "lib.php";
echo 'in library "'.__FILE__.'"&lt;br /&gt;';
?&gt;
</code></pre>

<p>file: lib.php</p>

<pre><code>&lt;?php
if( $_SERVER['SCRIPT_FILENAME'] != '/var/www/html/index.php')
{
    echo "Not allowed";exit;
} else 
{
    echo 'in library "'.__FILE__.'"&lt;br /&gt;';
    echo '&lt;pre&gt;';
    print_r($_SERVER);
    echo '&lt;/pre&gt;';
}
?&gt;
</code></pre>
