Input does not pass validation test for strlen - php

Question

I am making a login system and I have a form with some validation.
However my form seems to be failing to pass the validation even though the data input should pass easily.
See:
http://marmiteontoast.co.uk/fyp/login-register/index.php
When you input a username, it should be over 3 characters. But even if you enter one really long you get the error message: The username is less than 3 characters.
EDIT: There was an issue in my copying from formatting that caused a missing }. I've corrected this. It wasn't the issue.
This is the if statement for the username pass. So it seems like it is not getting past the first test:
if (isset($_POST['username'])){
$username = mysql_real_escape_string(trim($_POST['username']));
$_SESSION['status']['register']['username'] = $username;
if(strlen($username) > 3){
if(strlen($username) < 31){
if(user_exists($username) === true){
$_SESSION['status']['register']['error'][] = 'That username is already taken. Sorry, please try again with a different username.';
}else{
// passed
}
} else {
$_SESSION['status']['register']['error'][] = 'The username is greater than 30 characters.';
}
} else {
$_SESSION['status']['register']['error'][] = 'The username is less than 3 characters.';
}
} else {
$_SESSION['status']['register']['error'][] = 'The username is not entered.';
}
And this is the HTML for the username:
<form method="post" action="register.php">
<div class="username">
<label class="control-label" for="inputUser">Username</label>
<input type="text" id="inputUser" name="username" placeholder="Username" value="<?php echo $usern_value; ?>" />
</div>
You can see the site here: http://marmiteontoast.co.uk/fyp/login-register/index.php
Session
The index page does use sessions.
It starts with this:
<?php
session_start();
?>
And kills the session at the end of the file:
<?php
unset($_SESSION['status']);
?>
But in the file it starts new sessions which store the inputs. This is so if you make a mistake, it still holds your info so you can adjust it rather than having the fill in the form again. Here is an example of where it grabs the username and saves it, then outputs it.
<?php
if(isset($_SESSION['status']['register']['username'])){
$usern_value = $_SESSION['status']['register']['username'];
} else {
$usern_value = "";
}
?>
value="<?php echo $usern_value; ?>" />
This is the user-exists function:
function user_exists($username){
$sql = "SELECT `id` FROM `users` WHERE `username` = '".$username."'";
$query = mysql_query($sql);
$result = mysql_num_rows($query);
if($result == 1){
// username does already exist
return true;
}else{
// username doesn't exist in the database
return false;
}
}

Answer 1

Ah, I can see the problem from your website link. When the error pops up ("The username is less than 3 characters."), try refreshing your browser. I expected to receive a browser warning that says the data would be resubmitted to the server — because you are in a post form — but I did not.
So, what does this mean? It means that immediately after validation failure, you are redirecting back to the same screen, and — unless you are using a session to preserve this information — your $_POST data will be lost. Commonly in the case of validation failure with this sort of form, you must prevent that redirect and render inside the post operation, which keeps the user's input available to you. The redirect should only occur if the form input was successful (i.e. it saves to the data and/or sends an email).
Edit: I should have seen the $_SESSION in the original post. OK, so the strategy is to write things to the session, redirect regardless of validation outcome, and to save error messages to the session. I wonder whether you are not resetting the session errors array when you're posting the form? Immediately after your first if, try adding this:
if (isset($_POST['username'])){
$_SESSION['status']['register']['error'] = array(); // New line
Unless you have something to make the session forget your errors, they will be stored until you delete your browser's cookie.

Answer 2

You have missed a closing brace } on this line:
if(user_exists($username) === true){
} else{// **missed the closing brace before the else**
// passed
}

Answer 3

Why is your logic so complex?
if (strlen($username) < 3) {
// too short
} elseif (strlen($username) > 31) {
// too long
} elseif (true === user_exists($username)) {
// already registered
} else {
// passed
}