Php Variable is null when i pass it to the array - php

Question

I am trying to send user-specific web notifications with onesignal and i solved everything except this variable null problem.
I use that variable multiple times and there is no problem except these lines:
<?php
if(isset($_POST["sub"]))
{
$my_variable= $_POST["t1"];
$SQL = "some sql here";
if (mysqli_query($db, $SQL)) {
echo $my_variable;
echo "<br>";
function sendMessage(){
$content = array(
"en" => 'test message'
);
$fields = array(
'app_id' => "5b0eacfc-3ac8-4dc6-891b-xxxxx",
'filters' => array(array("field" => "tag", "key" => "key", "relation" => "=", "value" => "$my_variable")),
'data' => array("foo" => "bar"),
'contents' => $content
);
$fields = json_encode($fields);
print("\nJSON sent:\n");
print($fields);
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "https://onesignal.com/api/v1/notifications");
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json; charset=utf-8', 'Authorization: Basic xxxxxxx'));
curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
curl_setopt($ch, CURLOPT_HEADER, FALSE);
curl_setopt($ch, CURLOPT_POST, TRUE);
curl_setopt($ch, CURLOPT_POSTFIELDS, $fields);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
$response = curl_exec($ch);
curl_close($ch);
return $response;
}
$response = sendMessage();
$return["allresponses"] = $response;
$return = json_encode( $return);
The result is :
1 JSON sent: {"app_id":"5b0eacfc-3ac8-4dc6-891b-xxxxx","filters":[{"field":"tag","key":"key","relation":"=","value":"null"}],"data":{"foo":"bar"},"contents":{"en":"test message"}}
I tried so many variations with/without quotas , json_encode() function but couldn't pass that variable to that array.

Answer 1

Your variable is out of scope.
You define $my_variable outside of the function sendMessage(), but proceed to try and use it within the function, without passing it as a parameter.
This can be fixed with the following:
function sendMessage($filterValue)
{
$content = array(
"en" => 'test message'
);
$fields = array(
'app_id' => "5b0eacfc-3ac8-4dc6-891b-xxxxx",
'filters' => array(array("field" => "tag", "key" => "key", "relation" => "=", "value" => $filterValue)),
'data' => array("foo" => "bar"),
'contents' => $content
);
$fields = json_encode($fields);
print("\nJSON sent:\n");
print($fields);
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "https://onesignal.com/api/v1/notifications");
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json; charset=utf-8', 'Authorization: Basic xxxxxxx'));
curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
curl_setopt($ch, CURLOPT_HEADER, FALSE);
curl_setopt($ch, CURLOPT_POST, TRUE);
curl_setopt($ch, CURLOPT_POSTFIELDS, $fields);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
$response = curl_exec($ch);
curl_close($ch);
return $response;
}
$response = sendMessage($my_variable);
$return["allresponses"] = $response;
$return = json_encode( $return);