A small API for lilURL. Place in the same folder as your index.php. It uses a HTTP POST request for the long url and outputs a JSON string as response.

api.php

<?php

/* api.php - A small API hack for lilURL
 * Made in 2013 by @nilsding
 */

require_once 'includes/conf.php';
require_once 'includes/lilurl.php'; 

$lilurl = new lilURL();
$msg = '';

if ( isset($_POST['longurl']) )
{
	$longurl = trim(mysql_escape_string($_POST['longurl']));

	$protocol_ok = false;
	
	if ( count($allowed_protocols) )
	{
		foreach ( $allowed_protocols as $ap )
		{
			if ( strtolower(substr($longurl, 0, strlen($ap))) == strtolower($ap) )
			{
				$protocol_ok = true;
				break;
			}
		}
	}
	else
	{
		$protocol_ok = true;
	}
		
	if ( $protocol_ok && $lilurl->add_url($longurl) )
	{
		if ( REWRITE )
		{
			$url = 'http://'.$_SERVER['SERVER_NAME'].dirname($_SERVER['PHP_SELF']).$lilurl->get_id($longurl);
		}
		else 
		{
			$url = 'http://'.$_SERVER['SERVER_NAME'].$_SERVER['PHP_SELF'].'?id='.$lilurl->get_id($longurl);
		}

		$msg = '{"success": true, "status": "Successfully shortened url", "url": "'.$url.'"}';
	}
	elseif ( !$protocol_ok )
	{
		$msg = '{"success": false, "status": "Malformed URL (has to start with http:// or https://"}';
	}
	else
	{
		$msg = '{"success": false, "status": "Could not shorten URL due to an unknown error"}';
	}
}
else 
{
	$msg = '{"success": false, "status": "To use this URL shortener\'s API, you need to provide a POST parameter ' . 
	       '\'longurl\', which contains the URL which will be shortened by the service.", "exampleCURLCommand": ' .
	       '"curl -F longurl=\'http://twitter.com/nilsding\' http://'.$_SERVER['SERVER_NAME'].$_SERVER['PHP_SELF'].'"}';
}
echo $msg;
?>