PHP Tokenize a String by its length

Hi Web Masters,

Just wondering wether you can help us to come up with some tokenize
script.

My problem is wanted to display a LONG content into a short para (by
giving minimum letter lenght)

I mean if I have a 2 page content - just I want to display only 4 lines
having 200 letters then follows the content with "....." at the end of
short pera.

Can anybody help in this regards,
Thanks in advance

.