Question

I am having problems with an ajax login form. I am getting an a error from ajax saying that my username and password variables in my login_check.php file are undefined. Yet, when I initialize the variables to blank, the error goes away. The problem is, when I initialize the variables to blank, even if I put the right information into the login box, it will not let me log in. I am sure the problem is minor, but I just can’t see it. I just need the PHP and AJAX to work together and then I’m done. Thanks in advance.

login_check.php

<?php
require_once 'config.php';
require_once 'login.class.php';
$error = NULL;
$success = FALSE;

$username = $_POST['username'];
$password = $_POST['pass'];

$login = new Login();
//Connect to MYSQL Database server
$connect = mysql_connect(DB_HOST, DB_USER, DB_PASS) or die("Could not connect to MYSQL Database.");
$result = mysql_select_db(DB_NAME, $connect) or die("Could not connect to MYSQL table.");

//Clean Data to prevent malicous injections
$username = mysql_real_escape_string(strip_tags(stripcslashes(trim($_POST['username']))));
$password = $login -> encrypt(mysql_real_escape_string(strip_tags(stripcslashes(trim($_POST['pass'])))));

$sql = mysql_query("SELECT * FROM admin WHERE username = '$username' AND password = '$password'") or die("Query to database failed.");
$numrows = mysql_num_rows($sql);

$row = mysql_fetch_array($sql);
if ($numrows > 0) {
    session_start();
    $_SESSION['username'] = $row['username'];
    $success = TRUE;
    echo json_encode(array("success" => "Login successful."));

} else {

    $success = FALSE;
    echo $error = 'Invalid username or password!';
    echo json_encode(array("error" => "Invalid username or password! (PHP response)"));

}
?>

JQuery file

$('#login_form').submit(function(e) {

        e.preventDefault();

        var username = $('.username').val();
        var password = $('.password').val();

        $.ajax({
            type : "POST",
            url : "includes/login_check.php",
            data : "Username=" + username + "&Password=" + password,
            dataType : 'json',
            cache : false,
            success : function(data) {
                if(data.error) {
                    $('.login div.error').show().html(data.error);

                } else {
                    $('.login div.success').show().html(data.success);
                }

                //return false;

            },
            error : function(jqXHR, textStatus, errorThrown) {
                alert("error " + textStatus + ": " + errorThrown);
            },
            beforeSend : function() {
                $(".load").html("Loading...");
            }
        });

    });

By the way, the error from AJAX is:

error parsererror: SyntaxError: JSON.parse: unexpected character

Thank you again friends.

Answer 1

Several problems:

This:

$username = $_POST['username'];
$password = $_POST['pass'];

should be this:

$username = $_POST['Username'];
$password = $_POST['Password'];

Those keys have to match the parms you specified here:

data : "Username=" + username + "&Password=" + password,

…and even that should be changed to:

data : {"Username":username,"Password":password},

This line is producing invalid JSON:

echo $error = 'Invalid username or password!';

I think you meant to code just this?

$error = 'Invalid username or password!';

EDIT #1:

Also this line needs to be the very first thing in the PHP code:

session_start();