AJAX PHP Database NOT WORKING no errors - php

Question

I am new to AJAX and am trying to insert form data into a database using ajax and php. It is simply not working, I had errors to start off but now there are no more errors and the database doesn't update and there is no response text. Please Help!
AJAX
function submit(){
var vid = <?php echo $user['vid'] ?>;
var type = document.getElementById("type").value;
var rules = document.getElementById("rules").value;
var comments = document.getElementById("comments").value;
var xhttp;
if (window.XMLHttpRequest) {
xhttp = new XMLHttpRequest();
} else {
// code for IE6, IE5
xhttp = new ActiveXObject("Microsoft.XMLHTTP");
}
xhttp.onreadystatechange = function() {
if (xhttp.readyState == 4 && xhttp.status == 200) {
document.getElementById("page").innerHTML = xhttp.responseText;
}
}
xhttp.open("POST", "/content/training/request/submit.php", false);
xhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
xhttp.send("vid="+vid+"&type="+type+"&rules="+rules+"&comments="+comments);
}
</script>
PHP FILE AJAX IS CALLING:
<?php
require("http://".$_SERVER["HTTP_HOST"]."/config/db.php");
$stmt = $db->prepare("INSERT INTO trainingRequests (vid, type, rules, comments, timeSubmitted) VALUES (:vid,:type,:rules,:comments,:timeSubmitted)");
$stmt->bindParam(':vid', $vid);
$stmt->bindParam(':type', $type);
$stmt->bindParam(':rules', $rules);
$stmt->bindParam(':comments', $comments);
$stmt->bindParam(':timeSubmitted', $time);
$vid = $_POST["vid"];
$type = $_POST["type"];
$rules = $_POST["rules"];
$comments = $_POST["comments"];
$time = time();
$stmt->execute();
echo "Submitted!";

Answer 1

Don't use an HTTP URL in require. When you access the PHP script through the webserver, it runs the script (in another server instance, so it doesn't affect the current script), it doesn't return the script contents. Change it to:
require("../../config/db.php");