how to get unknown string in $_GET method through URL - php

Question

I want to pass a string from one PHP file to another using $_GET method. This string has different value each time it is being passed. As I understand, you pass GET parameters over a URL and you have to explicitly tell what the parameter is. What if you want to return whatever the string value is from providing server to server requesting it? I want to pass in json data format. Additionally how do I send it as Ajax?
Server (get.php):
<?php
$tagID = '123456'; //this is different every time
$tag = array('tagID' => $_GET['tagID']);
echo json_encode($tag);
?>
Server (rec.php):
<?php
$url = "http://192.168.12.169/RFID2/get.php?tagID=".$tagID;
$json = file_get_contents($url);
#var_dump($json);
$data = json_decode($json);
#var_dump($data);
echo $data;
?>

Answer 1

If I understand correctly, you want to get the tagID from the server? You can simply pass a 'request' parameter to the server that tells the server what to return.
EDIT: This really isn't the proper way to implement an API (like, at all), but for the sake of answering your question, this is how:
Server
switch($_GET['request']) {
case 'tagID';
echo json_encode($tag);
break;
}
You can now get the tagID with a URL like 192.168.12.169/get.php?request=tagId
Client (PHP with CURL)
When it comes to the client it gets a bit more complicated. You mention AJAX, but that will only work for JavaScript. Your php file can't use AJAX, you'll have to use cURL.
$request = "?request=tagID";
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, '192.168.12.169/get.php' . $request);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_TIMEOUT, '3');
$content = trim(curl_exec($ch));
curl_close($ch);
echo $content;
EDIT: added the working cURL example just for completeness.
Included cURL example from: How to switch from POST to GET in PHP CURL
Client (Javascript with AJAX)
$.get("192.168.12.169/get.php?request=tagId", function(data) {
alert(data);
});