login only works on localhost

[nickpartyka]

im just starting to learn php. im working on a basic login/user registration form and it works fine on localhost, but after i uploaded it to my server i get this error messag when i input correct login info:

Warning: mysql_num_rows( ): supplied argument is not a valid MySQL result resource in D:\Hosting\8927 368\html\EKMN\l ogin.php on line 53
The username you entered was not found.

here is my code:

<?php
error_reporting (E_ALL ^ E_NOTICE);
session_start();
$userid = $_SESSION['userid'];
$username = $_SESSION['username'];
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>username Login</title>
</head>
<body>
	<?php
	
	if($username && $userid){
		echo "Hey <b>$username</b>, you're already logged in! <a href='./member.php'>click here</a> for member page";

	}
	else{
		$form = "<form action='./login.php' method='POST'>
		<table>
		<tr>
			<td>Username</td>
			<td><input type='text' name='username' /></td>
		</tr>
		<tr>
			<td>Password</td>
			<td><input type='password' name='password' /></td>
		</tr>
		<tr>
			<td></td>
			<td><input type='submit' name='loginbtn'          value='login' /></td>
		</tr>
		<tr>
			<td><a href='./register.php'>Register</a></td>
			<td><a href='./forgotpass.php'>Forgot your password?</a></td>
		</tr>
		</table>
		</form>";
	 
		if ($_POST['loginbtn']){
			$username = $_POST ['username'];
			$password = $_POST['password'];
			
			if ($username){
				if($password){
					require("connect.php");
					
					$password = md5(md5("nt4ui2t".$password."gj4h3h"));
					// make sure login info is correct
					$query = mysql_query("SELECT * FROM users WHERE username='$username'");
					$numrows = mysql_num_rows($query);
					if ($numrows == 1){
						$row = mysql_fetch_assoc($query);
						$dbid = $row['userid'];
						$dbuser = $row['username'];
						$dbpass = $row['password'];
						$dbactive = $row['active'];
						
						if($password == $dbpass){
							if($dbactive == 1){
								// set session info
								$_SESSION['userid'] = $dbid;
								$_SESSION['username'] = $dbuser;
								
								echo "Hey <b>$dbid</b> <a href='./member.php'>click here</a> for member page";
								echo "<br />";
								echo "userid: ".$_SESSION['userid'];
							}
							else
								echo "You must activate your account before logging in.";
						}
						else
							echo "Wrong password!";
						
					}
					else
						echo "The username you entered was not found. $form";
					mysql_close();
				}
				else
					echo "You forgot your password! $form";
			}
			else
				echo "You forgot your username! $form";
		}
		else
			echo $form;
	}	
    ?> 
	

</body>
</html>

[AutumnsDecay]

A shot in the dark, but did you remember to set which database to use in your 'connect.php' file?

If you have more than one database running on your hosted server it could be confused.

If you didn't, try adding:

mysql_select_db('YourDB');

before your query.