$re = '~(\h*\(.*?(?:picture|see|lorem).*?\))~';
$str = 'Hello world (see below).
Lorem ipsum (there is a picture here) world!
Attack on titan (is lorem) great but (should not be removed).
Here is one(see should be removed too) world!
';
preg_match_all($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