PHP Delete Function not working - php

Question

Have had a look around but still struggling like no tomorrow. Just trying to get a delete button working. But its made complicated because the delete function is not completed on the one file.
Users are currently on the crud/view.php file
<?php
session_start();
if(isset($_SESSION['u_uid']))
$uid = $_SESSION['u_id'];
require_once('connect.php');
$ReadSql = "SELECT * FROM `contact` WHERE users_id=$uid ORDER BY Name";
$res = mysqli_query($connection, $ReadSql);
?>
I have a few functions but my delete button is:
<td> <input type="button" onClick="deleteme(<?php echo $r['u_uid']; ?>)" name="Delete" value="Delete"></td>
Followed by:
function deleteme(delid) {
if(confirm("Are you sure you want to Delete?")){
window.location.href='delete.php?del_id='+delid;
}
}
Leading to a crud/delete.php
<?php
session_start();
if(isset($_SESSION['u_uid'])){
require_once('connect.php');
$select = "DELETE from contact where id='".$_GET['del_id']."'";
$query = mysqli_query($connection, $select) or die($select);
}else {
print_r($_GET['del_id'])
?>
I think you can have the delete function on just the view.php and get rid of the delete.php. But I'm not sure what to do.
Many thanks!

Answer 1

Make sure that the variables really contain something that you expect it to have, does the u_uid was really set, try printing out your delete query to make sure that it builds a valid SQL statement.
Or you can try enclosing your table fields with back-ticks, like you did on your select statement.
It is very advisable also to use prepared statements to make your script more secured.