Complete my HMAC decryption in PHP

We are looking for a PHP version of the google HMAC encrypt method described in this link [login to view URL] Our supplier deliverd some keys to test the algorytm. e_key = aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa i_key = bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb data = qMgSYozqy_iTLthA_kqjsm_Y7PlGcHiO4UU9aw== I wrote a piece of code, but i can't find the answer why it is not working. Probably the php base64 encoding algorithm in PHP is not supporting RFC 3548. We’re looking for a work-around. Hereby our code //[login to view URL] function hmacEncrypt($price, $iv, $e_key, $i_key) { $pad = substr(hash_hmac('sha1', $iv, $e_key), 0, 8); $enc_price = $pad ^ $price; $signature = substr(hash_hmac('sha1', $price . $iv, $i_key), 0, 4); $final_message = base64_encode($iv . $enc_price . $signature); return $final_message; } function hmacDecrypt($final_message, $e_key, $i_key) { //$enc_price = base64_decode($final_message); $enc_price = base64_decode($final_message, 16); $iv = substr($enc_price, 0, 16); $signature = substr($enc_price, strlen($enc_price) - 4, 4); $p = substr($enc_price, 16, 8); $price_pad = substr(hash_hmac('sha1', $iv, $e_key), 0, 8); $price = $p ^ $price_pad; $conf_sig = substr(hash_hmac('sha1', $price . $iv, $i_key), 0, 4); return $price; if ($conf_sig === $signature) { return floatval($price); } } echo hmacDecrypt('qMgSYozqy_iTLthA_kqjsm_Y7PlGcHiO4UU9aw==', 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa', 'bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb');