Login Script: mysql_num_rows(): supplied argument is not a valid MySQL result resource

[David Hutto <dwightdhutto@xxxxxxxxx>]

The following script is supposed to validate a username and password in a mysql db.  When entering the username and password of a preregistered user, I get the following errors:

Warning:  mysql_num_rows(): supplied argument is not a valid MySQL result resource in /var/www/login.php on line 24



Warning:  Cannot modify header information - headers already sent by (output started at /var/www/login.php:24) in /var/www/login.php on line 26

On line 24 is:

>>>if(!mysql_num_rows($login)) //if the username and pass are wrong

--The supplied argument is $login, which is previously defined as:

>>>$login = mysql_query("SELECT * FROM 'userinfo' WHERE `user` = '$user' AND `pass` = '$pass`");

--which is further defined above it as these values:

  $user = $_POST['user']; //pulls the username from the form
  $pw = $_POST['pass']; //pulls the pass from the form
  $pass = md5($pw); //makes our password an md

So why is the sum of those previous definitions an invalid argument for the mysql_query() to test for whether the username and md5 password values are true/equivalent to each other?

Thanks for any help you may be able to provide, below is the full login.php page.

David
********************************************************

This is the full login.php script, I'm pretty sure no other portions are needed to show at this point for the current problem:

<?php
$act = $_GET['act']; //retrives the page action
if(empty($act)) //if there is no action
{
  echo('<form action="login.php?act=auth" method="post" name="loginform" id="loginform">
  <p>Username
  <input type="text" name="user">
  </p>
  <p>Password
  <input type="password" name="pass">
  </p>
  <p>
  <input type="submit" name="Submit" value="Login">
  </p>
  </form>');
}
elseif($act == "auth") //if our page action = auth
{
  $user = $_POST['user']; //pulls the username from the form
  $pw = $_POST['pass']; //pulls the pass from the form
  $pass = md5($pw); //makes our password an md5
  include("connect.php"); //connects to our mysql database
  $login = mysql_query("SELECT * FROM `userinfo` WHERE `user` = '$user' AND `pass` = '$pass`"); //selects info from our table if the row has the same user and pass that our form does
  if(!mysql_num_rows($login)) //if the username and pass are wrong
  {
        header("Location: login.php");  //redirects to our login page
        die(); //stops the page from going any further
  }
  else
  {
        setcookie("user", $user, time()+3600);//sets our user cookie
                setcookie("pass", $pass, time()+3600);//sets our pass cookie
                header("Location: memprar.php");//instead of yourpage.php it would be your protected page
  } 
}
?>