php - Regular expression that matches specific url format in textarea field -

basically want have html textarea field, user can write comment. if user writes url, want highlight url. example bellow:

"hi! comment. link http://www.google.com , comment continues."

i want regular expression match urls formatted follows:

i don't want match urls formatted follows

so far regular expression looks this:

/(http)?(s)?(:\/\/)?((w*\.)([a-za-z0-9])([-\w]+\.)+([^\s\.]+[^\s]*)+[^,.\s])/

but problem cannot match http://google.com (1) of list above.

i know topic may marked duplicate , apology wasn't able find need anywhere. appreciated :)

Ant COmde