bmspage/includes/update_event.php

<?php
        include "db_config.php";
$conn = mysqli_connect($servername, $username, $password, $db);

$event_id = mysqli_real_escape_string($conn, $_POST['event']);
$description = $_POST['description'];
$is_ongoing = mysqli_real_escape_string($conn, $_POST['is_ongoing']);
$end_date_time = mysqli_real_escape_string($conn, $_POST['end_date_time']);
$user = mysqli_real_escape_string($conn, $_POST['user']);

//Insert event to events table
$event = "UPDATE events SET description='$description', is_ongoing='$is_ongoing', date_time_end='$end_date_time', user='$user' WHERE event_id='$event_id'";

//Set variables for email
//MySQL queries to get Unit Name and Alert
$unitname_query = "SELECT unit_name FROM units AS units INNER JOIN events AS events ON events.unit_id=units.unit_id WHERE events.event_id=".$_POST['event']."";
$unitname_query_run = mysqli_query($conn, $unitname_query);
$unitname_array = mysqli_fetch_assoc($unitname_query_run);
$unitname = $unitname_array['unit_name'];

$alertname_query = "SELECT alert_name FROM alerts AS alerts INNER JOIN events AS events ON events.alert_id=alerts.alert_id WHERE events.event_id=".$_POST['event']."";
$alertname_query_run = mysqli_query($conn, $alertname_query);
$alertname_array = mysqli_fetch_assoc($alertname_query_run);
$alertname = $alertname_array['alert_name'];

$start_date_time_query = "SELECT date_time_start FROM events WHERE event_id=".$_POST['event']."";
$start_date_time_query_run = mysqli_query($conn, $start_date_time_query);
$start_date_time_array = mysqli_fetch_assoc($start_date_time_query_run);
$start_date_time = $start_date_time_array['date_time_start'];
//If successful, redirect back to index.php and send email, else tell user that it failed.
$result = mysqli_query($conn, $event);
if($result){
        echo("Event added, redirecting...");
        sleep (2);
        header('Location: ../index.php');
        //Set Email Info
        $to = "TO-EMAIL@DOMAIN.COM";
        $subject = "Updated BMS Alert: ".$unitname." ".$alertname."";
        $headers = "From: FROM-EMAIL@DOMAIN.COM";
        $message = "BMS Unit: ".$unitname." \n Type of Alert: ".$alertname." \n Start Date / Time: ".$start_date_time." \n End Date / Time: ".$end_date_time." \n Description: ".$description." \n Updated by: ".$user." \n Event Link: https://DOMAIN.com/bms/viewevent.php?eventid=$event_id \n \n This message generated by https://DOMAIN.com/bms";
        //WordWrap the message
        $message_wrapped = wordwrap($message, 70, "\n", true);
        //Send the email
        mail($to,$subject,$message_wrapped,$headers);
} else{
        echo('Error! Please <a href="javascript:history.back()">go back</a> and try again');
}
        $conn->close();
?>