$re = '/\[(?<key>\S+)\s+"(?<value>[^"]+)/m';
$str = ' 2020/03/01-10:01:01 [firstname "JOHN"] [surename "DOE"] [age "30"] [state "NY"] [id "10001"]
2020/03/01-10:01:02 [firstname "Julie"] [age "58"] [state "AU"] [id "10002"]
2020/03/01-10:01:02 [firstname "MEGAN"][middlename "myra"] [surename "DOE"] [age "58"] [state "AU"] [id "10052"]';
preg_match_all($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