How regular expressions match two situations

How regular expressions Match two cases
My links exist in these two cases

1, $str =xxx.php?a=aaa;
2, $str =xxx.php?a=aaa&m=bbb;

I wrote the regular, but can not match, ask the master to help write:

Preg_match ("/(. *?\.php) \? (. *))(? (&.*)) /is ", $str, $arr);


Desired result: When there is &m=xxx behind the link, the results here are also segmented, not exist just configure the front
------to solve the idea----------------------
You mean, if the second case is taken out of the BBB, the first case is taken out of AAA, right?
------to solve the idea----------------------
Why not parse_url it? Combine explode to analyze how many parameters are in your query that are more efficient than regular
------to solve the idea----------------------
1, $str =xxx.php?a=aaa;
2, $str =xxx.php?a=aaa&m=bbb;
Do not have a hard set of regular and sometimes it is not convenient
$val =end (explode (' = ', $str));

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