AJAX success result according to PHP if statement

Question

I have login form with submit button which calls Javascript function, in that function I call PHP file with AJAX. On PHP side I check if username, email and password are correct and then I return results to div with class Result. I need to return PHP check result and make further actions in javascript, my code:

PHP:

if (isset($_POST['username_or_email']) && isset($_POST['password'])) {
    $username_or_email = mysqli_real_escape_string($conn, $_POST['username_or_email']);
    $password_post = mysqli_real_escape_string($conn, $_POST['password']);

    $sql = "SELECT `password` FROM `users` WHERE `username` = '".$username_or_email."' OR `email` = '".$username_or_email."' LIMIT 1";
    $result = mysqli_query($conn, $sql);
    $row = mysqli_fetch_assoc($result);
    /* Check if username or email exists */
    if (mysqli_num_rows($result) > 0) {
        echo "valid_user";
    } else {
        echo "invalid_user";
    }
    /* Check if password is correct */
    if (password_verify($password_post, $row['password'])) {
        echo 'valid_pass';
    } else {
        echo 'invalid_pass';
    }
    $conn->close();
} 

JQUERY:

success: function (data) {
        if (data == "invalid_user") {
            $(".result").fadeIn(500).html("Incorrect username or email.");
        }
        if (data == "invalid_pass") {
            $(".result").fadeIn(500).html("Incorrect password.");
        }
        if (data == "valid_pass") {
           $(".result").fadeIn(500).html("Success, redirecting to account.");

           setTimeout(function() {
              document.location.href = 'nextpage.php';
           }, 2500);
        }
     }

So my questionis: how to make check on JQUERY side properly if I have several IF statements on PHP side. After user press login button I want to show that username or pass is correct/incorrect and which one is correct/incorrect, it is needed just for information purpose.

Answer 1

The best way is to create an array of elements in your PHP file and store all the information you need. For example:

$info=array("user"=>"valid","password"=>"invalid");

Then, convert the array into a JSON string and simply echo it:

echo json_encode($info);

Once the data is retrieved, you can easily manipulate them by converting them into a javascript array of elements like this:

info=JSON.parse(data);

NOTE: PHP can only "communicate" with Javascript via Strings. JSON Strings is the most commonly used way of achieving such results, due to it's simplicity.