PHP PDO statement that checks for existing username - php

Question

currently working on an application and curious as to why my script is going to a blank page once I submit my form. It started occurring when I added a piece to my script that is supposed to go into my database that checks if a username exists and then echos a message if that is the case and echos a message if it isn't the case.
This is the code:
function validateUser() {
global $user, $userErr, $validForm;
$userErr = "";
if ($user == "") {
$userErr = "nothing entered";
$validForm = false;
}
else if (!preg_match("/^[a-zA-Z]+(([\'\,\.\- ][a-zA-Z ])?[a-zA-
Z]*)*$/",$user)) {
$userErr = "invalid characters";
$validForm = false;
}
elseif (strlen($user) > 1) {
$stmt = $conn->prepare("SELECT COUNT(username) AS num FROM credentials WHERE
username = :username");
$stmt->bindValue(':username', $user);
$stmt->execute(array($user));
$norows = $result->fetchColumn();
if ($norows > 0 ) {
$userErr = 'Username already taken';
}
else {
$userErr='User added';
}
}
}
The bit that is giving me trouble is the last elseif statement... for some reason it hasn't been doing what it's supposed to do. I've looked at many different sources and I've tried implementing different solutions but nothing has seemed to work. This function runs when the form is submitted just incase you are wondering. Very open to any possible solutions you may have. Because I just can't get it to work... thanks!

Answer 1

Don't Use else if() since you are using different comparison statements. Just replace all your else if() with if() only. Then use $userErr variable to check if the inputs pass all your validations.
function validateUser() {
global $user, $userErr, $validForm;
$userErr = "";
if ($user == "") {
$userErr = "nothing entered";
$validForm = false;
}
if (!preg_match("/^[a-zA-Z]+(([\'\,\.\- ][a-zA-Z ])?[a-zA-Z]*)*$/",$user)) {
$userErr = "invalid characters";
$validForm = false;
}
if (strlen($user) > 1) {
$stmt = $conn->prepare("SELECT COUNT(username) AS num FROM credentials WHERE
username = :username");
$stmt->bindValue(':username', $user);
$stmt->execute(array($user));
$norows = $result->fetchColumn();
if ($norows > 0 ) {
$userErr = 'Username already taken';
}
}
if($userErr == "") {
$userErr='User added';
}
}