Warning on pack() in the push notifications script

I'm writing my push notifications script in PHP. the $deviceToken is correct, but I've a warning in this line:

$b = pack('H*', str_replace(' ', '', $deviceToken));

the warning is this:

Warning: pack() [function.pack]: Type H: illegal hex digit in /myurl.com/send_push_notification.php on line 33

And the notification doesn't arrive.

Do you know why?

I had the same problem. I ended up using

trim($device_token)

instead of

str_replace(' ', '', $deviceToken)

Fixed the issue in the end.

I had the same problem. Finally, I found that there was a space character in my URL! So, just check your URL, perhaps that's the error.

I also suffered from the same problem. It solved my issue. try using below code:

chr(0) . chr(0) . chr(32) . pack('H*', str_replace(' ', '', $item[0])) . chr(0) . chr(strlen($payload)) . $payload;  

If anyone is still having this issue, try

$deviceToken = pack('H*', str_replace(' ', '', sprintf('%u', CRC32($deviceToken))));