In its very simplest form, the session code would look something like this:

Code:

if ($submit_x === '0' || $submit_x > 0) {
   // form submitted
              
   if (!$user || !$pass ) {
      header("Location: $PHP_SELF?err=1");
      exit;
   }
                    
   $user = trim(stripslashes($user));
   $pass = trim(stripslashes($pass));
                 
   $query = "SELECT `password` FROM `tUsers` WHERE userid = '$user' AND `isActive`=1";
   $result = mysql_query($query);
   if ($result) {
      if (mysql_num_rows($result) > 0) {
         $myrow = mysql_fetch_array($result);
         if ($myrow["password"]) {
            $dbpass = $myrow["password"];              
         } else {
            header("Location: $PHP_SELF?err=2");
            exit;
         }         
      } else {
         header("Location: $PHP_SELF?err=2");
         exit;
      }
   } else {
      header("Location: $PHP_SELF?err=3");
      exit;
   }
        
        
   // compare given pass with real pass
   if ($pass == $dbpass) {
         
      // store the details in session variables
      session_start();
      session_register("SESSION");
      session_register("SESSION_USERID");            
                        
      // assign values to the session variables
      $SESSION_USERID = $user;                      
                                                              
      // redirect user to the list page
      header("Location: index.php");
   }  else {
      header("Location: $PHP_SELF?err=2");
   }
}
?>
<html>
<head>
</head>
<body>
<?php
if ($err) {
   if ($err == 1) {
      print "<div id="errMsg">You did not enter a username or password.  Please try again.</div>";
   }
   if ($err == 2) {
      print "<div id="errMsg">Username or password incorrect.  Please try again.</div>";
   }
   if ($err == 3) {
      print "<div id="errMsg">Database error.  Please try again later.</div>";
   }
}
?>

<div id="loginForm>
   <form name="login" method="POST" action="<?php echo $PHP_SELF ?>">
      <label for="user">Username</label><input type="text" name="user" tabindex="1" />
      <label for="pass">Password</label><input type="password" name="pass" tabindex="2" />
      <input type="image" src="submitbutton.gif" value="Submit" tabindex="3" name="submit" />
      <input type="image" src="clearbutton.gif" value="Clear" tabindex="4" name="clear" />
   </form>
</div>
</body>
</html>