gistfile1.php

<?php

$required = array('hostname', 'username', 'password', 'database', 'driver');
$config = array(
    'password'  => 'pass',
    'database'  => 'mydb',
    'charset'   => 'utf8',
    'port'      => '1234'
);
$errors = array_diff($required, array_flip($config));
$last = array_pop($errors);
$errmsg = 'Missing required configurations. No %s or %s has been configured';
var_dump(sprintf($errmsg, implode(', ', $errors), $last));

What stuff is it you think I should scratch? :)

@oaass starting with the second comment I said unapplicable stuff to this code. Using $last could become dangerous and the principles I've outlined after the second comment would kick in, only if you use that variable for some "business logic", and not just error string formatting.

For instance, if you would also be doing:

if($last == 80) {
    //assuming that $last is always the port number
}

@flavius yeah I agree $last can a "dangerous" variable for this. This was just for showing. It also requires for two elements to be missing as well. But it was just to illustrate that this was simpler than array_map. I wasn't actually able to make array_map work in this situation, which was why I looked elsewhere for a solution.