How do I double check my PHP signin form

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I made a signin form that will look through the database and find a match to the user's credentials, but how do I fix this code so it will relocate the page if there is no match.



 include_once 'includes/dbh.php';

 $username = $_POST['u_name'];
 $password = $_POST['pwd'];

 $sql = "SELECT * FROM users;";
 $result = mysqli_query($conn, $sql);

 while ($row = mysqli_fetch_assoc($result)) {
     if ($username == $row['username'] && $password == $row['password']) {
         $_SESSION['username'] = $username;
         header("Location: second_index.php?signinSuccessful");
     if ($username != $row['username'] && $password != $row['password']) {
         header("Location: index.php?NotSucessful");

I tried putting the code inside of the loop, but I know that can't work, and if I put it outside of the loop, It redirects even if the credentials are correct. Please help. Thanks

First of all, this is totally wrong, you're looping trough all the users to see if the user exist, instead of that sql statement try $sql = "SELECT * FROM users where user='$user' and password='$password'";

And to avoid any data breach in that sql statemen you have to serialize the user and pass like that before adding it to the statement

$user =  mysql_real_escape_string($conn, $user);
$password =mysql_real_escape_string($conn, $password);

Then you only check if the fields aren't empty (which means the user exist)

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You are getting all the users from the users table and checking each record manually in php. The reason why your code doesn't work is because the while loop doesn't check all the users in user table. If the first record in the retrieved table data doesn't match with entered username and password, it will go to 2nd if block and redirect.

You should change your query to filter by user-entered values.


And later check in php if any record is returned. If any record is returned, it is a valid user, else redirect the user to failed authentication page.

As a good practice, make sure to use parameterized query.

Update Replace the while loop and block with this.

if(mysqli_num_rows($result) > 0){ 
    // valid user
    // invalid user

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Why do you need while loop in this case when you fetching data from database? Using sql and make the database fetch the only one correct answer, don't make server site do unnecessary work. I propose just do simple fetch then if check, no need for while loop at all. Your logic is always redirect to index.php when username password not correct so of course it will always do so when your while loop on server do not hit the correct user.

Secure Login System with PHP and MySQL, Learn how to create your own secure login system with PHP, MySQL, HTML5, Now we check if the data from the login form was submitted, isset() will If you get an error make sure to double-check your code to make sure  As I said in my answer, there's no foolproof check to see if an email exists. Not every server will tell you an account is invalid if you try to send an email to it and if you start spamming a server with junk test requests it can get you blacklisted (i.e. Spamhaus, etc) – Machavity Apr 19 '15 at 12:57

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PHP MySQL Login Tutorial - Check if Username Exists, In another PHP MySQL login tutorial I'll teach you how to check if the users username exists Duration: 7:49 Posted: Jul 28, 2012 Php login script is used to provide the authentication for our web pages. the Script executes after submitting the user login button. Login Page. Login page should be as follows and works based on session. If the user close the session, it will erase the session data.

  • how do I check if the record is returned using this method?
  • Use if instead of while
  • How do I use the if statement? I'm not sure how to check if the return isn't false
  • Update the answer. Check it out.
  • I have exactly what you had, but I'm getting this error