+ $refererHost = parse_url($referer, PHP_URL_HOST);
+ if (!empty($referer) && (strpos($refererHost, $host) !== false || startsWith('?', $refererHost))) {
+ $finalReferer = $referer;
+ }
+
+ return $finalReferer;
+}
+
+/**
+ * Validate session ID to prevent Full Path Disclosure.
+ *
+ * See #298.
+ * The session ID's format depends on the hash algorithm set in PHP settings
+ *
+ * @param string $sessionId Session ID
+ *
+ * @return true if valid, false otherwise.
+ *
+ * @see http://php.net/manual/en/function.hash-algos.php
+ * @see http://php.net/manual/en/session.configuration.php
+ */
+function is_session_id_valid($sessionId)
+{
+ if (empty($sessionId)) {
+ return false;
+ }
+
+ if (!$sessionId) {
+ return false;
+ }
+
+ if (!preg_match('/^[a-zA-Z0-9,-]{2,128}$/', $sessionId)) {
+ return false;
+ }
+
+ return true;
+}
+
+/**
+ * In a string, converts URLs to clickable links.
+ *
+ * @param string $text input string.
+ * @param string $redirector if a redirector is set, use it to gerenate links.
+ *
+ * @return string returns $text with all links converted to HTML links.
+ *
+ * @see Function inspired from http://www.php.net/manual/en/function.preg-replace.php#85722
+ */
+function text2clickable($text, $redirector)
+{
+ $regex = '!(((?:https?|ftp|file)://|apt:|magnet:)\S+[[:alnum:]]/?)!si';
+
+ if (empty($redirector)) {
+ return preg_replace($regex, '<a href="$1">$1</a>', $text);