$re = '/\[click here]\(http[^()]*\)(*SKIP)(*F)|(?:https?:\/\/)?(?:[^.]+\.)?momento360\.com\/e\/(.*)/m';
$str = '[click here](https://momento360.com/e/uc/1478291a8dd94a8198339f1ffe4b97be?utm_campaign=embed&utm_source=other&size=medium)
https://momento360.com/e/u/a9b53aa8f8b0403ba7a4e18243aabc66
https://momento360.com/e/uc/1478291a8dd94a8198339f1ffe4b97be?upload-key=e84e1fb3567546a885a2a223bde6ef32';
preg_match_all($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