$re = '/(.*)p\.PERSONAL=[^&]*(.*)/';
$str = 'zeit.BUCHUNGSTAG=[2017-11-01T00%3A00%3A00;2018-02-01T23%3A59%3A59]&_viewjoins=zeit|ba|ma|p&p.PERSONAL=in[deil_felix;lechner_carina]&fdf=dfuebfek
p.PERSONAL=in[deil_felix;lechner_carina]&zeit.BUCHUNGSTAG=[2017-11-01T00%3A00%3A00;2018-02-01T23%3A59%3A59]&_viewjoins=zeit|ba|ma|p';
preg_match_all($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