smsgateway.me store message status in php variable - php

Question

Using smsgateway.me to send a message I use the default code with my own variables which are working fine. However, sometimes the SMS does not send and I would like to store the SMS in the database if failed.
To do so I think I need a value from the $result array, but I dont know how to start. I tried many different codes without any result.
Can anywone please tell me how to get an if sent ok -> do something / else do something else based on the code and variables below?
Thanks a lot!
Documentation here
Here is the default code (with default variables) that sends a message:
<?php
include "smsGateway.php";
$smsGateway = new SmsGateway('demo#smsgateway.me', 'password');
$deviceID = 1;
$number = '[phone]';
$message = 'Hello World!';
$options = [
'send_at' => strtotime('+10 minutes'), // Send the message in 10 minutes
'expires_at' => strtotime('+1 hour') // Cancel the message in 1 hour if the message is not yet sent
];
//Please note options is no required and can be left out
$result = $smsGateway->sendMessageToNumber($number, $message, $deviceID, $options);
?>
Success content:
{
"success": true,
"result": {
"success": [
{
"id": "308",
"device_id": "4",
"message": "hello world!",
"status": "pending",
"send_at": "1414624856",
"queued_at": "0",
"sent_at": "0",
"delivered_at": "0",
"expires_at": "1414634856",
"canceled_at": "0",
"failed_at": "0",
"received_at": "0",
"error": "None",
"created_at": "1414624856",
"contact": {
"id": "14",
"name": "Phyllis Turner",
"number": "[phone]"
}
}
],
"fails": [
]
}
}
error content:
{
"success": true,
"result": {
"success": [
],
"fails": [
"number": "[phone]"
"message": "hello world!",
"device": 1
"errors": {
"device": ["The selected device is invalid"],
}
]
}
}

Answer 1

This did the trick if failed:
if (isset($result['response']['result']['fails'][0]['number']) === TRUE) {
echo 'failed';
else{
echo 'success';
}
this works on success:
if(isset($result['response']['result']['success'][0]['id']) === TRUE){
echo 'success';
}else{
echo 'failed';
}
Thanks Michael, your reply helped me to change it a bit and figure it out!