pack() in php. Illegal hex digit warning

Question

i am having some problems using pack() in php

$currencypair = \"EUR/USD\";
$buy_sell = \"buy\";
$alert_device_token =array(\"a\",\"a\",\"b\");
$message = \"         


        

Answer 1

In this case, $alert_device is an array.

For packing it needs a value.

Use pack('H*', str_replace(' ', '', $alert_device[0])) instead.