gistfile1.php

<?php

$user = function($name) {
    $me = array();

    $me['name'] = NULL;

    $me['init'] = function($name) use(&$me) {
        $me['name'] = $name;
        return $me;
    };

    $me['whoami'] = function() use(&$me) {
        return $me['name'];
    };

    return $me['init']($name);
};

$foo = $user('foo');

$bar = $user('bar');
$bar['say'] = function() {
    return 'Hello';
};

$name = $foo['whoami']();
var_dump($name);
var_dump(isset($foo['say']));

$name = $bar['whoami']();
var_dump($name);
var_dump($bar['say']());