Right way to go about logging in...

Ok, basically, I taught myself PHP by reading tutorials and taking apart other people's code, not sure if other people have done the same, but anyway... No doubt, a lot of the code I used to taught myself was old and/or outdated.

When I'm approaching login, this is basically what I do.

<?php
$ln = md5( $_POST['login_name'] );
$pa = md5( $_POST['password'] );

$query = "SELECT * FROM `members` WHERE `login_name` = '{$ln}' AND `password` = '{$pa}'";
$result = mysql_query( $query );

if( $result )
{
    echo( 'Login successful.' );
}
else
{
    echo( 'Login unsuccessful.' );
}
?>

Now that's all fine and dandy and it has always worked for me, but now I've started to use classes and functions it doesn't work out.

<?php
$ln = md5( $_POST['login_name'] );
$pa = md5( $_POST['password'] );

$db->select( '*', 'members', array( 'mem_lname' => $ln, 'mem_pass' => $pa ) );
$db->exec_query();

/*
$exec_query performs mysql_query() on the query created with $db->select and returns it within $db->result

Now the problem is, the following statement always evaluates to true
*/

if( $db->result )
{
    echo( 'Login successful.' );
}
else
{
    echo( 'Login unsuccessful.' );
}

/*
If I get rid of the above statement and do this:

$db->fetch_assoc();
var_dump( $db->assoc );

...it works as expected, so my query is well formed and is being executed

echo( $db->result );

would produce a resource id, unless of course I enter incorrect details and $db->assoc contains all the data from the database, again, unless I enter incorrect details.
*/
?>

So what should I do to check if the login was successful, now that if( $db->result) doesn't work?

This approuch is floored.

<?php
$ln = md5( $_POST['login_name'] );
$pa = md5( $_POST['password'] );

$query = "SELECT * FROM `members` WHERE `login_name` = '{$ln}' AND `password` = '{$pa}'";
$result = mysql_query( $query );

if( $result )
{
    echo( 'Login successful.' );
}
else
{
    echo( 'Login unsuccessful.' );
}
?>

mysql_query returns true if your query is successfull, not if it finds results. There is a difference.

You would need to use...

<?php

$ln = md5( $_POST['login_name'] );
$pa = md5( $_POST['password'] );

$query = "SELECT * FROM `members` WHERE `login_name` = '{$ln}' AND `password` = '{$pa}'";
if ($result = mysql_query( $query )) {
  if(mysql_num_rows($result)) {
    echo( 'Login successful.' );
  }
  else
  {
    echo( 'Login unsuccessful.' );
  }
}
?>

Other than that, theres not much we can help you with. Simply stating something doesn't work gives us nothing. We need to see the relevent code.