$re = '/views\.decorators\.cache\.cache_(?:page|header)\.([[:alnum:]]+)\.(?:GET\.)?([[:alnum:]]+)(?:\.[[:alnum:]]+)?\.en-us\.UTC/m';
$str = 'views.decorators.cache.cache_header.APISetOne.596e986edcf211a323dbac38fe3654b8.en-us.UTC
views.decorators.cache.cache_page.APISetTwo.GET.1fc365e1f67d39935b199c133fada23b.ce596bddd33104b703521c71eb2e32c6.en-us.UTC';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php