Dont use numeric keys in arrays

Ok, example. I write extension for viewtopic.php and need rewrite param 0 in array $pun_page['user_ident']. What i be do, if somebody in another extension put new param to $pun_page['user_ident'] like array_unshift()?

array_unshift($pun_page['user_ident'], 'Lexazloy stupid!');

Please, use associations arrays:
$pun_page['user_ident']['avatar'], $pun_page['user_ident']['username'], etc. in viewtopic.php another files.

$pun_page['user_ident'][] = 'some';
$pun_page['user_ident'][] = 'another some';
$pun_page['user_ident'][] = 'another another some';

Realy not good.

upd please.