$re = '/https?:\/\/my\.matterport\.com\/show\/\??(m=(?<code>[\w\d]+))/m';
$str = 'https://my.matterport.com/show/?m=kiVrPJ4GLGF&brand=0&ts=2
https://my.matterport.com/show/?m=8QLBuW5dxqB&brand=0&ts=3&help=1
https://my.matterport.com/show/?m=vycyVs9Xe9W';
preg_match_all($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