请教如何在delpih中使用HMAC-SHA1算法

* @brief 使用HMAC-SHA1算法生成oauth_signature签名值
*
* @param $key 密钥
* @param $str 源串
*
* @return 签名值
*/
function getSignature($str, $key) {
$signature = "";
if (function_exists('hash_hmac')) {
$signature = base64_encode(hash_hmac("sha1", $str, $key, true));
} else {
$blocksize = 64;
$hashfunc = 'sha1';
if (strlen($key) > $blocksize) {
$key = pack('H*', $hashfunc($key));
}
$key = str_pad($key, $blocksize, chr(0x00));
$ipad = str_repeat(chr(0x36), $blocksize);
$opad = str_repeat(chr(0x5c), $blocksize);
$hmac = pack(
'H*', $hashfunc(
($key ^ $opad) . pack(
'H*', $hashfunc(
($key ^ $ipad) . $str
)
)
)
);
$signature = base64_encode($hmac);
}

return $signature;
}