mysqli注册脚本，检查用户或电子邮件是否存在

Question

Check accepted answer if you have a simular issue.

First of all, i know there are a few simular questions like this but non of them where able to help me.

I'm trying to check if username or email is already in the database, i already have them set to unique in the database, but want this so i can show seperate errors for username / email.

Right now it just outputs a white page when trying to register and i have spent hours trying to figure it out by myself.. any help will be highly appreciated.

I added comments around the problematic code i cant get to work.

This is my code:

<?php
// Include database connection and functions here.
include 'db_connect.php';
include 'functions.php';

// The hashed password from the form
$password = $_POST['p'];
// Create a random salt
$random_salt = hash('sha512', uniqid(mt_rand(1, mt_getrandmax()), true));
// Create salted password (Careful with the chilli)
$username = $_POST['username'];
$email = $_POST['email'];



//Start of problematic code

$check_stmt = $mysqli->prepare("SELECT * FROM members WHERE username=? OR email=?");
$check_stmt->bind_param('ss', $username, $email);
$check_stmt->execute();
$check_result = $check_stmt->get_result();
while ($row = $check_result->fetch_assoc()) {
    if ($row->num_rows > 0)
    {
        if ($row['username'] > '')
        {
            header("Location: '..\..\..\?RegUserExsist=1'");
        }
        else if ($row['email'] > '')
        {
            header("Location: '..\..\..\?RegEmailExsist=1'");
        }
    }

//end of problematic code



    else if(!filter_var($email, FILTER_VALIDATE_EMAIL))
    {
        header("Location: '..\..\..\?RegInvalidEmail=1'");
    }
    else if (empty($username))
    {
        header("Location: '..\..\..\?RegInvalidUser=1'");
    }
    else if (empty($password))
    {
        header("Location: '..\..\..\?RegInvalidPass=1'");
    }
    else
    {
$password2 = hash('sha512', $password.$random_salt);

if ($insert_stmt = $mysqli->prepare("INSERT INTO members (username, email, password, salt) VALUES (?, ?, ?, ?)"))
{
$insert_stmt->bind_param('ssss', $username, $email, $password2, $random_salt);
// Execute the prepared query.
$insert_stmt->execute();

header("Location: '..\..\..\?success=1'");

}
else
{
header("Location: '..\..\..\?regfailed=1'");
}}}
?>

Answer 1

I use PDO and I have this code which checks to see if a username has already been taken

<?php    
/* Create a new PDO object with database connection parameters */
    $dbh = new PDO('mysql:host='.DB_HOST.';dbname='.DB_NAME.'', DB_USER, DB_PASS);

    // Create statement object
    $stmt = $dbh->prepare("SELECT username FROM users WHERE username = :username");

    $stmt->bindValue(":username", $user);

    $stmt->execute();

    if($stmt->rowCount() != 0) {
        $this->setError('<span class="bold">Username</span> you have selected has already been used by another member in our database. Please choose a different Username!');
    }