Question

I’m running the following code, but everything it gives me the following errors. I’ve read several articles on SO, still no use.
The error I’m getting is:

Warning: mysql_fetch_assoc(): supplied argument is not a valid MySQL result resource in /home/xyz/public_html/13/beta/signup.php on line 49
Warning: Cannot modify header information - headers already sent by (output started at /home/xyz/public_html/13/beta/signup.php:49) in /home/xyz/public_html/13/beta/signup.php on line 69

My PHP script:(I’ve marked the lines 49 & 69)

if(isset($_POST['submit'])&&$_POST['submit']=='Login')
{
    $err = array();
    if(!$_POST['username'] || !$_POST['pass'])
        $err[] = 'All the fields must be filled in!';

    if(!count($err))
    {
        $_POST['username'] = mysql_real_escape_string($_POST['username']);
        $_POST['pass'] = mysql_real_escape_string($_POST['pass']);
        $_POST['remember'] = (int)$_POST['remember'];

        $row = mysql_fetch_assoc(mysql_query("SELECT id,user,email,clg FROM users WHERE user='{$_POST['username']}' AND pass='".md5($_POST['pass'])."'"));-->line 49

        if($row['user'])
        {

            $_SESSION['user']=$row['user'];
            $_SESSION['id'] = $row['id'];
            $_SESSION['clg'] = $row['clg'];
            $_SESSION['email'] = $row['email'];
            $_SESSION['remember'] = $_POST['remember'];
            setcookie('tcookie',$_POST['remember']);
            header("Location: index.php");
            exit;
        }
        else $err[]='Wrong username and/or password!';
    }

    if($err)
    $_SESSION['msg']['login-err'] = implode('<br />',$err);

    header("Location: signup.php");-->line 69
    exit;
}

Answer 1

Your mysql_query function is returning an error, instead of a result. Try:

$res = mysql_query("SELECT id,user,email,clg FROM users WHERE user='{$_POST['username']}' AND pass='".md5($_POST['pass'])."'");
if ($res === false) {
    echo mysql_error();
    die;
}
$row = mysql_fetch_assoc($res);

This will help you get the error information.

Once that error is gone, you’ll probably find that the ‘headers already send error’ disappears too, it’s a consequence of something already being printed to the output (possibly an error message).

---

Update: For your ‘No database selected’ error, you need to use mysql_select_db($databasename); before you use mysql_query(). Otherwise, mysql has no idea which database you’re trying to query.

Also, you may want to look into using PDO, it’s another way of accessing MySQL databases, and it’s heaps more secure and a bit easier to use (IMO).