Jan Goyvaerts, Regex Guru, has addressed this issue in his blog. There are quite a few caveats, for example extracting URLs inside parentheses correctly. What you need exactly depends on the "quality" of your input data.
For the examples you provided, \b(?:(?:https?|ftp|file)://|www\.|ftp\.)[-A-Z0-9+&@#/%=~_|$?!:,.]*[A-Z0-9+&@#/%=~_|$] works when used in case-insensitive mode.
So to find all matches in a multiline string, use
preg_match_all('/\b(?:(?:https?|ftp|file):\/\/|www\.|ftp\.)[-A-Z0-9+&@#\/%=~_|$?!:,.]*[A-Z0-9+&@#\/%=~_|$]/i', $subject, $result, PREG_PATTERN_ORDER);
$result = $result[0];
