字符的二进制，php的pack与unpack

$curl = curl_init ();
curl_setopt($curl, CURLOPT_URL ,  'https://mh.18touch.com/restful/magic');
curl_setopt($curl, CURLOPT_PORT, 80);
//curl_setopt($curl, CURLOPT_CONNECTTIMEOUT_MS, 50);
//curl_setopt($curl, CURLOPT_TIMEOUT_MS, 50);
//curl_setopt($curl, CURLOPT_HEADER, true);
//curl_setopt($curl, CURLINFO_HEADER_OUT , true);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($curl, CURLOPT_FOLLOWLOCATION, 0);
curl_setopt($curl, CURLOPT_POST, true);
//$p_data=file_get_contents('xyl.zip');

$p_data ="test 123";
$data_length = strlen($p_data);

for($i=0;$i<$data_length;$i++){
	$byte[] = pack('H2',dechex(ord($p_data[$i])));
}
$str = implode('',$byte);
$data_length = strlen($str);
$p_data =$str;

curl_setopt($curl, CURLOPT_HTTPHEADER, array("Content-Length: $data_length","Content-Type: application/octet-stream"));
curl_setopt($curl, CURLOPT_POSTFIELDS, $p_data);
//curl_setopt($curl, CURLOPT_NOBODY , true);
$a = curl_exec($curl);
//$b = curl_getinfo($curl);
var_dump($a);
$curl = curl_init ();
curl_setopt($curl, CU