adult content censoring

hi... i have to make an adult content censoring system so people cant post "bad" words on any public viewable posts. i know preg_replace and possibaly preg_match would be a huge help but im wondering how i would put all the bad words in a file (textfile) 1 word on a line and have it look through the file for the words? when it finds a match then it will either replace the word with * but better yet tell the user that content in the post was rejected because of bad content and take them back to the form with the stuff they typed in it... if there is a better way to do this (i hope sounds like a lot of work)....