Receive UDP packet datagrams in PHP

I am working in php to build a listening server for a GPS tracking system. The GPS sends data through UDP packets, which I can display by running the below script. However the actual data comes out in symbols so I am guessing I am missing a conversion

    //Reduce errors
    error_reporting(~E_WARNING);

    //Create a UDP socket
    if(!($sock = socket_create(AF_INET, SOCK_DGRAM, 0)))
    {
        $errorcode = socket_last_error();
        $errormsg = socket_strerror($errorcode);

        die("Couldn't create socket: [$errorcode] $errormsg \n");
    }

    echo "Socket created \n";

    // Bind the source address
    if( !socket_bind($sock, "192.168.1.29" , 1731) )
    {
        $errorcode = socket_last_error();
        $errormsg = socket_strerror($errorcode);

        die("Could not bind socket : [$errorcode] $errormsg \n");
    }

    echo "Socket bind OK \n";

    //Do some communication, this loop can handle multiple clients
    while(1)
    {
        echo "\n Waiting for data ... \n";

        //Receive some data
        $r = socket_recvfrom($sock, $buf, 512, 0, $remote_ip, $remote_port);
        echo "$remote_ip : $remote_port -- " . $buf;

            //Send back the data to the client
        //socket_sendto($sock, "OK " . $buf , 100 , 0 , $remote_ip , $remote_port);

    }

    socket_close($sock);