FM/nixtape/utils/licenses.php

<?php
define('BY1',     1);
define('BY2',     2);
define('BY21',    3);
define('BY25',    4);
define('BY3',     5);
define('BYSA1',   6);
define('BYSA2',   7);
define('BYSA21',  8);
define('BYSA25',  9);
define('BYSA3',  10);
define('LAL',    11);
define('PD',     12);
define('CC0',    13);

// Arrays containing regular expressions for each license type
// (so we can support multiple URL formats in the future if needed)
$by1 = array('http://creativecommons.org/licenses/by/1.0/?.*');
$by2 = array('http://creativecommons.org/licenses/by/2.0/?.*');
$by21 = array('http://creativecommons.org/licenses/by/2.1/?.*');
$by25 = array('http://creativecommons.org/licenses/by/2.5/?.*');
$by3 = array('http://creativecommons.org/licenses/by/3.0/?.*');
$bysa1 = array('http://creativecommons.org/licenses/by-sa/1.0/?.*');
$bysa2 = array('http://creativecommons.org/licenses/by-sa/2.0/?.*');
$bysa21 = array('http://creativecommons.org/licenses/by-sa/2.1/?.*');
$bysa25 = array('http://creativecommons.org/licenses/by-sa/2.5/?.*');
$bysa3 = array('http://creativecommons.org/licenses/by-sa/3.0/?.*');
$lal = array('http://artlibre.org/licence.php/lal.html');
$pd = array('http://creativecommons.org/licenses/publicdomain/?.*');
$cc0 = array('http://creativecommons.org/publicdomain/zero/?.*');

// map licenses to ids by array position
$licenses = array(array(), $by1, $by2, $by21, $by25, $by3, $bysa1, $bysa2, $bysa21, $bysa25, $bysa3, $lal, $pd, $cc0);

function simplify_license($license) {
	global $licenses;

	foreach ($licenses as $key => $l) {
		foreach ($l as $urlschema) {
			if (preg_match("|$urlschema|", $license)) {
				return $key;
			}
		}
	}

	return 0;
}

/**
 * Returns true if the supplied license is one that we accept as being free
 *
 * @param $license string containing a license URL
 * @return bool whether this license is free or not
 */
function is_free_license($license) {
	global $licenses;

	foreach ($licenses as $key => $l) {
		foreach ($l as $urlschema) {
			if (preg_match("|$urlschema|", $license)) {
				return true;
			}
		}
	}

	return false;
}