What is a more elegant solution to these nested if/elseif statements?

Question

I'm building a website that contains users with user profiles. Many of the fields in the profile are optional.

There is an opportunity for a lot of user-generated content, and so I need to display the author of this content in many different locations of the site (comments, posts, etc.). In the user's profile, he is able to (optionally) fill out his "first name", his "last name", and a "display name".

To display the author, I wrote a helper method that looks through a provided array of these fields and returns the most appropriate name for the user, in this order of preference:

1. If the user filled out display_name, this will be displayed.
2. If the user filled out first_name and last_name, but no display_name, it will display both names
3. If the user only filled out first_name, it will display first_name.
4. If the user only filled out last_name, it will display last_name.
5. If all else fails, a user id will be displayed i.e. user123
6. If none of the array keys are present, or the parameter is NULL, the name will display as NULL

The method works great, but it's ugly. There must be a way to beautify this with an alternative to nested if/else statements.

public function nameify($names = NULL) {
    $name = '';
    if (!empty($names)) {
        if (!empty($names['display_name'])) {
            $name = $names['display_name'];
        } elseif (!empty($names['first_name'])) {
            $name = $names['first_name'];
            if (!empty($names['last_name'])) {
                $name .= ' ' . $names['last_name'];
            }
        } elseif (!empty($names['last_name'])) {
            $name = $names['last_name'];
        }

        if (empty($name) && !empty($names['id'])) {
            $name = 'user' . $names['id'];
        } else {
            $name = 'NULL';
        }
    } else {
        $name = 'NULL';
    }
    return $name;
}

Answer 1

public function nameify($names = NULL) {
    if ($names) {
        if (!empty($names['display_name'])) {
            return $names['display_name'];
        }
        if (!empty($names['first_name'])) {
            $name = $names['first_name'];
        } 
        if (!empty($names['last_name'])) {
            $name .= ' ' . $names['last_name'];
        }
        if (empty($name) && !empty($names['id'])) {
            $name = 'user' . $names['id'];
        }
    }
    return $name ? ltrim($name) : 'NULL';
}

Set the default first, and return that if nothing else matches. Then since we always want to return the display name if we have it do just that.

EDIT: Tweak to prevent returning "NULL "

Answer 2

Using ternary conditions we can shorten and beautify the code:

public function nameify($names = NULL) {
    $name = 'NULL';

    if (!empty($names)) {

        $name = ($names['display_name']) ? $names['display_name'] : trim($names['first_name']." ".$names['last_name']);

        if(!$name) $name = ($names['id'] > 0) ? 'user'.$names['id'] : 'NULL';
    }

    return $name;
}