Does anyone have a PHP snippet of code for grabbing the first "sentence" in a string?

If I have a description like:

"We prefer questions that can be answered, not just discussed. Provide details. Write clearly and simply."

And all I want is:

"We prefer questions that can be answered, not just discussed."

I figure I would search for a regular expression, like "[.!\?]", determine the strpos and then do a substr from the main string, but I imagine it's a common thing to do, so hoping someone has a snippet lying around.