title: Can't log in as registered user (php and mysql)
body: <p>I'm trying to do a log in and registration script. I've managed to finish most of it; however, after I register a user I am unable to log in as that user. That is, registered users are unable to log in. Any help would be massively appreciated! :) </p>
  
  <p>This is the code that relates to the specific problem:</p>
  
  <pre><code>$login = login ($username, $password);
          if ($login === false) {
           $errors [] = 'That username/password combination is incorrect';
          } else {
             $_SESSION ['user_id'] = $login;
             header ('Location: index.php');
             exit (); 
      }       
  
  
  function  login ($username, $password) {
     $user_id = user_id_from_username ($username);
  
     $username = sanitize ($username);
     $password = md5($password);
  
  return (mysql_result(mysql_query("SELECT COUNT(user_id) FROM users WHERE username =     '$username' AND password = '$password'"), 0) == 1) ? $user_id : false;
  }
  </code></pre>
  
  <p>I wrote the query above like this (BELOW), earlier. Writing it this way allowed me to log in but with "literally" any password. </p>
  
  <pre><code>function login ($username, $password){ 
    $user_id = user_id_from_username ($username);
  
    $username = sanitize ($username); 
    $password = sanitize ($password); 
  
    $query1 = mysql_query("SELECT COUNT(user_id) FROM users WHERE username =     '$username'"); 
  
   $query2 =  mysql_query("SELECT COUNT(user_id) FROM users WHERE password = '$password'"); 
  
   return  (mysql_result($query1, 0) == 1) ? $user_id : false; 
   return (mysql_result($query2, 0) == 1) ? $user_id : false;
  </code></pre>
  
  <p>That is to say, I broke the query down into two parts, but noticed the password query was completely irrelevant (even if I "commented" it out).</p>
  
  <p>PS. I know I should be using PDO or Mysqli instead of mysql queries, and that md5 isn’t that secure.  Just ignore these things for the sake of this riddle. </p>