$re = '/\[test\].*(?=\<br\s\/\>)/m';
$str = '\'This is a test to remove single lines.<br />
The line below has the open type bbcode (case insensitive) that is to be removed.<br />
The text on the same line that follows the bbcode should also be removed.
this text should remain[test]this text should be removed on this line only!<br />
the other lines should remain.<br />
done.<br />\'';
preg_match($re, $str, $matches, PREG_OFFSET_CAPTURE, 0);
// Print the entire match result
var_dump($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