Get and operate with answer from other server in php - php

Question

I'm trying to make some sort of communication between two servers(can be called license verification).
Already got this:
index.php
if ($verification == 1) {
echo "license validated";
}
else {
echo "this license key does not exist.";
}
validate.php
$license_key = mysql_real_escape_string($_GET['license_key']);
$query = "SELECT license_key FROM users WHERE license_key = '$license_key'";
$mysqli = new mysqli();
$mysqli->connect($db_hostname, $db_username, $db_password, $db_name);
if ($mysqli->connect_errno) {
echo "Failed to connect to MySQL: " . $mysqli->connect_error;
}
$result = $mysqli->query($query);
$row_cnt = $result->num_rows;
if ($row_cnt == 1) {
return true;
}
else {
return false;
}
What I can't figure out is how to send that request from index.php to validate.php ( this 2 files are not in same server ) and how to get back to index.php information what it returns (true or false).

Answer 1

Use file_get_contents:
$verify_result = file_get_contents("http://validation.domain.com/validate.php?license_key=$key");
if ($verify_result == 'license validated') {
...
}

Answer 2

Probably the easiest way would be to setup a service. Here's one of numerous tutorials out there.
For example, let's say that the validation server's hostname is val.com. You could setup a service there that looks like:
val.com/validation/validate?dataToValidae=<validationString>
Be sure to send the request over SSL if you don't want it to be intercepted.
You could then have the service return whether or not the validation succeeded, and then check for that in your code.