I have a bit of a strange situation.

What I want to be able to do is if a html form is submitted have a php include() or something that would callup a seperate external website url and look for an instance of the phrase Invalid user credentials on the html/jsp page and if that phrase does not exsist on the page then redirect the user to a specified url otherwise display a error message to the page. However I don't want to display any content from the page I am including.

Not sure if the above makes sense what I want to do. The goal is to enable people to be logged into two different websites by filling out one html form. And I am not able to remotely connect to the seperate websites database most I can do is feed the seperate website a users username/pass via the address bar since that site uses a $_GET[] to recieve the user cridentials to authenticate.

There is file_get_contents which should work for urls too. If that doesn't work, you could use curl. Then there is strpos which you can use to check if the string is inside those contents. Hope that helps.