}
}
+/*
+ This function aims to generate cryptographically strong random identifier.
+ Result identifier has length 4[strength/8/3]
+*/
+function random_id($strength = 128)
+{
+ $n = ceil($strength/8);
+
+ if (function_exists('openssl_random_pseudo_bytes'))
+ $bin = openssl_random_pseudo_bytes($n, $cstrong); // openssl on php 5.3 and up
+ else if (file_exists('/dev/urandom'))
+ $bin = file_get_contents('/dev/urandom', false, null, -1, $n); // linux std random device
+ else {
+ $bin = '';
+ for($i=0; $i < $n; $i++)
+ $bin .= chr(mt_rand(0, 255)); // Mersene Twister generator
+ }
+ $id = strtr(base64_encode($bin), '+/=', '-_x'); // see RFC 4648 Section 5
+
+ return $id;
+}