PHP - named params

<?php

function namedArgs1(array $args)
{
    extract($args, EXTR_PREFIX_ALL, '_');

    unset($args);

    if (isset($__firstname, $__lastname)) {
        return $__firstname . ' ' . $__lastname;
    }
}

function namedArgs2(array $args)
{
    $firstname =& $args['firstname'];
    $lastname =& $args['firstname'];

    if (isset($firstname, $lastname)) {
        return $firstname . ' ' . $lastname;
    }
}

function namedArgs3(array $args)
{
   $get_args = function($token) use($args) {

        $token = strtok($token, '.');
        $return =& $args;
        while($token !== false){
            $return =& $return[$token];
            $token = strtok('.');
        };

        return $return;
   };

   return $get_args('firstname') . ' ' . $get_args('lastname');
}

echo namedArgs1(['firstname' => 'Wallace', 'lastname' => 'de Souza']);
echo namedArgs2(['firstname' => 'Wallace', 'lastname' => 'de Souza']);
echo namedArgs3(['firstname' => 'Wallace', 'lastname' => 'de Souza']);