Trying to reduce memory usage of script - php

Question

I am a math teacher who has built an online testing site for my school to use (aka, not a pro). The site has worked well but as the amount of usage at my school increases I am starting to run into memory problems (I think). After I have about 50 to 60 users simultaneously using the site the whole website begins to crash, it will come back up after a few minutes. I never have this problem with low usage. The page where students take their quiz loads 10 questions on the page, each multiple choice with 4 radio options. (Not a lot of jquery going on). Each time the user clicks an answer I am using ajax to store their answer in the database. Below is the jquery code that sends their clicks as they take the quiz.
$('input:radio').click(function(){
var questionId = $(this).parent().parent().find('.qid').val();
var answer = $(this).val();
$.ajax({
type: "POST",
url: "insertqanswerajax.php",
data: {questionId: questionId, answer: answer},
});
});
When I load system process in my cpanel I see there are 5 different processes running, each around 80 megabytes. The maximum in my php.ini is set to 540MB. If I check the page with memory_get_peak_usage() it never reads above about half a megabyte, however in the console timeline I can see the memory usage is almost up to 10 megabytes for one user (images below). What do I need to check, or what is the best way to troubleshoot the discrepancy? What could be causing the problems? I can provide more information if needed, I am just not sure what all is relevant.
Thanks ahead of time for your help.
Here is the code for the php file accessed via ajax
<?php session_start();
include('../includes/startup.php');
$questionId = $_POST['questionId'];
$answer = $_POST['answer'];
insertQuizAnswer($questionId, $userId, $answer, 1);
?>
The function called in that file:
function insertQuizAnswer($questionId, $userId, $answer, $testId){
global $DB;
$standardsHandle = $DB->prepare("INSERT INTO quizanswers (questionid, userid,answer,testid)
VALUES (:questionId,:userId, :answer, :testId)
");
$standardsHandle->bindParam(':questionId', $questionId);
$standardsHandle->bindParam(':userId', $userId);
$standardsHandle->bindParam(':answer', $answer);
$standardsHandle->bindParam(':testId', $testId);
$standardsHandle->execute();
}
And the startup file loaded on both:
<?php
if(preg_match('/(?i)msie [2-7]/',$_SERVER['HTTP_USER_AGENT']))
{
// if IE < 8
echo "My Class Progress does not Work with this version of Internet Explorer</br>
<a href='https://www.google.com/intl/en/chrome/browser/'>Click Here to Download a more modern browser</a>";
exit;
}
else
{
}
if(isset($_POST['getGrade'])){
$_SESSION['gradeLevel'] = $_POST['getGrade'];
}
if(isset($_POST['getSubject'])){
$_SESSION['subject'] = $_POST['getSubject'];
}
include_once('../functions/userfunctions.php'); //all functions
include_once('../functions/goalfunctions.php'); //all functions
include_once('../functions/modulefunctions.php'); //all functions
include_once('../functions/globalfunctions.php'); //all functions
include_once('../functions/skillfunctions.php'); //all functions
include_once('../functions/quizfunctions.php'); //all functions
include_once('../functions/practicefunctions.php'); //all functions
include_once('../functions/benchmarkfunctions.php'); //all functions
include_once('../functions/dockfunctions.php'); //all functions
include_once('../functions/dashboardfunctions.php'); //all functions
include_once('../functions/notificationfunctions.php'); //all functions
include_once('../includes/connect.php'); //connect to database
$userSubject = $_SESSION['subject'];
$userGradeLevel = $_SESSION['gradeLevel'];
$userId = $_SESSION['userId'];
if ($_SESSION['loggedIn'] == 'true'){
}
else{
header('location: ../../index.php');
die();
}
?>
Here is the connect.php file that is accessed:
try {
$DB = new PDO("mysql:host=$host;dbname=$dbname", $user, $pass);
}
catch(PDOException $e) {
echo $e->getMessage();
}

Answer 1

The amount memory used is dependent on ini_set('memory_limit'); This amoutn is reserved by Apache, it doesn't matter how much the script actually uses until it runs out of memory.