PHP & MySQL: How do I compare the user input to data in the database?

Question

I have a HTML form with a textbox where you enter a username, and a login button. When the user presses the login button, I want the database to be queried and if there is a match echo out a statement. The code I have is this:

<form class="login_box" method="POST">
        <input id="input-boxes1" type="text" name="username" value="" placeholder="Username">
        <input id="button-1" type="submit" name="login" value="Login">
    </form>


// Checks if login button is pressed
    if (isset($_POST['login'])) {
      $enteredUser = $_POST['username'];

      $sql = "SELECT * FROM user WHERE username='$enteredUser'";
      if ($result = mysqli_query($link, $sql)) {
          echo 'it works';
      }
    }

What I want it to do is echo out "it works" if there is a match. However it always echoes it out no matter what. The database is working as intended as I have added to it and selected from it in other files, and the database is correctly linked to this form as well.

Any help would be great, thanks!

Answer 1

Thank you to @El_Vanja and @droopsnoot for helping. I've managed to figure out the solution now. As they rightly pointed out, I had to see if the number of rows returned was 1 and then echo out the statement if so.

My amended code is as below:

if (isset($_POST['login'])) {
      $enteredUser = $_POST['username'];

      $sql = "SELECT * FROM user WHERE username='$enteredUser'";
      $result = mysqli_query($link, $sql);
      if (mysqli_num_rows($result) == 1) {
          echo 'it works';
      }
}