需要考虑给定字符串之前和之后的PHP空格进行字节处理

I need to send 8 bytes to a given server in my socket.

The string should have 8 bytes with 3 characters and 5 empty spaces. However, PHP always strips out the spaces. How could i go about this?

<?php
   $SERVICE_NAME = "PXA     "; //8 bytes
   $OPT = "CODE5";

   $sendBytes = $SERVICE_NAME . $OPT;

   //i need sendBytes to go as PXA     CODE5
   //instead it goes as PXA CODE5.     

   $mySocket->send($sendBytes);
?>