Question

What control structures can one use instead of multiple nested IF statements.

eg:

function change_password($email, $password, $new_password, $confirm_new_password)
{
    if($email && $password && $new_password && $confirm_new_password)
    {
        if($new_password == $confirm_new_password)
        {
            if(login($email, $password))
            {
                if(set_password($email, $new_password))
                {
                    return TRUE;
                }
            }
        }
    }
}       

This function is used like this:

if(!change_password($email, $password, $new_password, $confirm_new_password)
{
    echo 'The form was not filled in correctly!';
    exit;
}

I call all my functions like this, and I’m wondering if there’s something wrong with my coding style. I’m having my doubts because if I follow this design then that means every single function I write will just be with nested with IF’s, checking if there are errors at every stage. Is this what other people do?

I don’t see many other scripts written like this, with the nested IF’s making a triangle shape and only having the desired result in the very middle. If the middle isn’t reached, then something screwed up.

Is this a good function structure?

Answer 1

Nesting too deeply is generally a bad idea – it’s spaghetti logic and difficult to follow. Since each of your verification steps depends on the previous stage having succeeded, don’t nest at all – just bail out when a stage fails:

function change_password(blah blah blah) {
   if (!$condition1) {
      return false;
   }
   if (!$condition2) {
      return false;
   }
   etc....


   // got here, must have succeeded
   return true;
}

That makes it explicitly clear what the logic sequence is.