However, since you are not doing anything that requires the use of a regular expression, I would just use explode():
$t = explode("\r\n", trim($l));
(Although from the variable name "$lines", it at least sounds a bit strange that there would be carriage-return/newlines within each line, especially after trim()-ing any that might be at the end of the line?)
"Please give us a simple answer, so that we don't have to think, because if we think, we might find answers that don't fit the way we want the world to be."
~ Terry Pratchett in Nation