Warning message with user authentication script

[ant_the_mus]

I got this code from dev cough.. Devarticles cough. It all works fine except I get this warning message:

Warning: Unable to jump to row 0 on MySQL result index 2 in c:\inetpub\wwwroot\login.php on line 11


quite new to php so not sure whats causing it, but Im real sure one of you good people will enlighten me [img]images/smilies/yawnb.gif[/img]

Heres the code

<?PHP 
$db = mysql_connect('localhost', 'Ant_the_mus', 'pass') or die("Couldn't connect to the database." ); 
mysql_select_db('Jokes') or die("Couldn't select the database" ); 
// Add slashes to the username, and make a md5 checksum of the password. 
$_POST['user'] = addslashes($_POST['user']); 
$_POST['pass'] = md5($_POST['pass']); 
$result = mysql_query("SELECT userId FROM users WHERE userPass='$_POST[pass]' AND userName='$_POST[user]'" ) or die("Couldn't query the user-database." ); 
$num = mysql_result($result,0); 
if (!$num) { 
// When the query didn't return anything, 
// display the login form. 
echo "<h3>User Login</h3> 
<form action='$_SERVER[PHP_SELF]' method='post'> 
Username: <input type='text' name='user'><br> 
Password: <input type='password' name='pass'><br><br> 
<input type='submit' value='Login'> 
</form>"; 
} else { 
// Start the login session 
session_start(); 
// We've already added slashes and MD5'd the password 
$_SESSION['user'] = $_POST['user']; 
$_SESSION['pass'] = $_POST['pass']; 
// All output text below this line will be displayed 
// to the users that are authenticated. Since no text 
// has been output yet, you could also use redirect 
// the user to the next page using the header() function. 
// header('Location: page2.php'); 
echo "<h1>Congratulations</h1>"; 
echo "You're now logged in. Try visiting <a href="page2.php">Page 2</a>."; 
} 
?>

[DR_LaRRY_PEpPeR]

that would mean the query didn't return any rows and therefore there is no row 0 in in the mysql_result() line. i'd change the query line and the if() to this

<?php

$result = mysql_query("SELECT 1 FROM users WHERE userPass='$_POST[pass]' AND userName='$_POST[user]'" )
    or die("Couldn't query the user-database."); 

if (!mysql_num_rows($result)) {

?>

[ant_the_mus]

Hey thanks for that fix DR_LaRRY_PEpPeR. I appreciate it! Though Id be even more gratefull if you wouldnt mind sharing with me some explanation so I might learn something from it.

especially the select 1 from users which is something Ive not seen before and the mysql_num_rows function

Cheers

[DR_LaRRY_PEpPeR]

sure, always good to know how things work.

i just changed the query to SELECT 1 because all you're wanting to do is see if there's a row that matches the WHERE. you don't really need to SELECT the userID for any reason. writing 1 is just the simplest thing to put for checking if a row exists.

the mysql_num_rows() then simply checks to see if a row was returned. it will return 0 and therefore be false if no matching row was found.

does that explain it?

[ant_the_mus]

Sure does,

thanks again