- var_dump: documentation ( source)
- preg_match: documentation ( source)
<?php
$p = "oauth2provider.server.main.grant_type.";
preg_match('~^oauth2provider.server(?:.([a-zA-Z0-9_]+))(?:.(grant_type|storage))(?:.([a-zA-Z0-9_]+))*$~', $p, $m);
var_dump($m);