$re = '/(https?:\/\/)?+(www)?([^:\/]+\.)?mysite\.[a-zA-Z]{1,3}/m';
$str = 'dsad
https://www.google.ee
http://www.mysite.com
www.mysite.ee
https://mysite.au
mysite.io
dsa kdadas das das www.google.com fsafsa fasf as
dsadasdas http://google.com
dasd
';
preg_match_all($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