Problems updating MySQL, "username" in a table using PHP - php

Question

I'm probably not using the best method to create a user system, but it doesn't need to be fancy. I also know that I'm not the most organized
The logins and everything are alright, but I'm having a problem updating the credentials.
For example, I'm allowing users to change their username. I have the "Change Username" (Not that name) form to submit to update-username.php.
I already have mysql_real_escape_string, in the function "cleanString" in another page. My textarea submitting already has the old text in it, so you can change and view it before hand.
$user_id = "";
if(isset($_POST['id']))
{
$user_id = $_POST['id'];
}
$query = "SELECT username,email,display_name,access,password FROM users WHERE user_id='$user_id'";
$results = mysql_query($query);
if(!$results) { //Check to see if query failed
die(mysql_error());
}
$resultsfetch=mysql_fetch_array($results);
$username = $resultsfetch['username'];
$usernamenew = $_POST['usernameinput'];
if(isset($_POST['usernameinput'])) {
$usernamenew = cleanString($_POST['usernameinput']);
}
if($usernamenew !=$username){
$submit = "UPDATE users SET username = '$usernamenew' WHERE user_id = '$user_id'";
mysql_query($submit);
if(!$submit) { //Check to see if query failed
die(mysql_error());
}
}
It's probably something stupid or simple that I missed, or something really huge. Mainly because I am absent minded.

Answer 1

$submit = sprintf("UPDATE users SET username = '%s' WHERE user_id = %d",mysql_real_escape_string($usernamenew),mysql_real_escape_string($user_id));

Answer 2

If the page is loaded, $user_id will be NULL so noting will be updated! Make sure that this page loads, by sending $_POST['id'] . if these things are correct, check this.
"Did the database user have any permission to update the table? "

Answer 3

I have re-arranged your code. added comments where i changed. Try this
if (isset($_POST['id'], $_POST['usernameinput'])) { // Check if both POST id and usernameinput is available
$user_id = (int)$_POST['id']; //assuming this is an integer
$query = "SELECT username,email,display_name,access,password FROM users WHERE user_id='$user_id'";
$results = mysql_query($query);
if (!$results) {//Check to see if query failed
die(mysql_error());
}
if (mysql_num_rows($result) > 0) { //verify if there is really a user with such id
$resultsfetch = mysql_fetch_array($results);
$username = $resultsfetch['username'];
$usernamenew = cleanString($_POST['usernameinput']);
if ($usernamenew != $username) {
$submit = "UPDATE users SET username = '$usernamenew' WHERE user_id = '$user_id'";
if (!mysql_query($submit)) {//Check to see if query failed
die(mysql_error());
}
}
}else{
die("no such user with userid=$user_id");
}
}
Warning: mysql_ function is deprecated as of PHP 5.5.0, and will be removed in the future. Instead, the MySQLi or PDO_MySQL extension should be used.

Answer 4

So, I guess I figured it out. It's an issue with my code carrying over to the next page.
The code I had been shown only broke the page, whether it be missing an integer, or something else. I'm not 100% sure.
Thanks for all the help guys, but now I know the issue.
EDIT:
I had forgotten to echo the $user_id in my hidden field.