PHP Script Unknown Error - php

Question

I have a registration form that the user enters data in. Then after it is posted to the same page and checked for null fields, the variables are put in the $_SESSION array and the user is directed to another form to enter another set of data in a table. After posting those variables, the variables from the previous page are extracted from $_SESSION and the new values are checked for null entries. After they are checked in a for loop, php script mysteriously stops (die("<h1> GOT HERE! </h1>") no longer appears on the screen) and the page keeps loading. After waiting for a while the page reloads itself.
I've been using die() for a while now to find the error, but it just doesn't echo between the for-loop and the if statement, and there is no apparent reason why it shouldn't. Here have a look:
<?php
session_start();
function sanitize($data) {
$data = trim($data);
$data = stripslashes($data);
$data = htmlspecialchars($data);
return $data;
}
if($_SESSION["registering"] != 1){
die("This page is to be used only when registering. Go to home page and select the seminar you want and click Register");
}else if($_SESSION["registered"] == 1){
die("You have already registered. Thank you. You can no longer access this page. To view your registration report, click here. ");
}else{
$id = sanitize($_SESSION["id"]);
$attendees = sanitize($_SESSION["attendees"]);
$ref_code = sanitize($_SESSION["Ref_Code"]);
$email = sanitize($_SESSION["email"]);
$prefix = sanitize($_SESSION["prefix"]);
$first_name = sanitize($_SESSION["first_name"]);
$last_name = sanitize($_SESSION["last_name"]);
$company = sanitize($_SESSION["company"]);
$address1 = sanitize($_SESSION["address1"]);
$address2 = sanitize($_SESSION["address2"]);
$user_city = sanitize($_SESSION["city"]);
$phone = sanitize($_SESSION["phone"]);
$responsibility = sanitize($_SESSION["responsibility"]);
$who_referred = sanitize($_SESSION["who-referred"]);
$role = sanitize($_SESSION["role"]);
$server = "MYREAL_DATABASE_SERVER";
$username = "CORRECT_USERNAME";
$password = "CORRECT_PASSWORD";
$dbname = "DB_NAME";
$conn = new mysqli($server, $username, $password, $dbname);
$query = "
SELECT *
FROM Seminar_Detail
WHERE Detail_id = '". $id ."'
";
$result = $conn->query($query);
if($result->num_rows == 0 ){
header("Location: ManagementSeminars.php");
}
$seminar = $result->fetch_assoc();
$name = $seminar["Seminar_Name"];
$city = $seminar["City"];
$from = $seminar["From"];
$to = $seminar["To"];
$fee = '';
$query = "SELECT Value FROM Fee WHERE Seminar_Name = '". $name ."' AND Currency = 'GBP'";
$result = $conn->query($query);
if($result->num_rows > 0){
$row = $result->fetch_assoc();
$fee = $row["Value"];
}
if($_SERVER["REQUEST_METHOD"] == "POST"){
$terminate = 0;
for($i = 1; i < ($attendees + 1); $i++){
if(isset($_POST["prefix-".$i]) && isset($_POST["first_name-".$i]) && isset($_POST["last_name-".$i]) && isset($_POST["position-".$i])){
$terminate = 0;
}else{
$terminate = 1;
}
}
die("<h1>".$terminate."</h1>");
if($terminate != 1){
$server = "SERVER";
$username = "USERNAME";
$password = "PASSWORD";
$dbname = "DBNAME";
$conn = new mysqli($server, $username, $password, $dbname);
$query = "
INSERT INTO Registry (Seminar_Name, Number_Attendees, Email, Prefix, First_Name, Last_Name, Company, `Address 1`, `Address 2`, City, Phone, Responsibility, Role, Who_Referred, Ref_Code)
VALUES ('". $name ."', '". $attendees ."', '".$email."', '".$prefix."', '".$first_name."', '".$last_name."', '".$company."', '".$address1."', '".$address2."', '".$user_city."', '".$phone."', '".$responsibility."', '".$role."', '".$who_referred."', '".$ref_code."')
";
$conn->query($query);
//ignore this part please
/*$query = "SELECT Registry_ID FROM Registry WHERE Ref_Code = '". $_SESSION["Ref_Code"] ."'";
$result = $conn->query($query);
$row = $result->fetch_assoc();
$registry_id = $row["Registry_ID"];
$attendee_first_name = "";
$attendee_last_name = "";
$attendee_position = "";
$stmt = $conn->prepare("
INSERT INTO Attendee (First_Name, Last_Name, Position, Registry_ID)
Values (?, ?, ?, ?)
");
$stmt->bindParam("ssss", $attendee_first_name, $attendee_last_name, $attendee_position, $registry_id);
for($i = 1; $i < $_SESSION["attendees"] + 1; $i++){
$attendee_first_name = sanitize($_POST["first_name-".$i]);
$attendee_last_name = sanitize($_POST["last_name-".$i]);
$attendee_position = sanitize($_POST["position-".$i]);
$stmt->execute();
}*/
}else{
$errorMessage = "<div class='alert alert-danger alert-dismissable'>
<strong>Oops!</strong> You have not entered all values.
</div>";
}
}
}
?>
I am positive that it is not a syntax error. Any help is appreciated!

Answer 1

The problem might be in this line
for($i = 1; i < ($attendees + 1); $i++){
You missed $ sign in i. It should be:
for($i = 1; $i < ($attendees + 1); $i++){
Having used error reporting, would have signaled an undefined constant i notice.
Add error reporting to the top of your file(s) which will help find errors.
<?php
error_reporting(E_ALL);
ini_set('display_errors', 1);
// rest of your code
Sidenote: Error reporting should only be done in staging, and never production.