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

I was having the same issue when developing a hybrid app using Ionic/Cordova/PhoneGap. As the same code is run in Android and iOS devices, I had made a mistake of storing Google FCM token as APNS token. The APNS token is purely hexadecimal but Google FCM token can have non-hexadecimal characters. So, packing a Google FCM token using PHP's pack() function will result in the illegal hex digit error.