Checking for variations of a name

[emrys404]

Hello, i'm writing some contact management software where the user will input a business name and some contacts. The problem arises when i want to allow only one instance of the business name to be entered. Variations between business names make this difficult. For instance a user could enter: Joe's Plumbing, Inc. or Joes Plumbing or Joes Pluminbing inc.
My initial attempt at this was to strip away all punctuation then break it down into single words and run "LIKE word1 and LIKE word2" etc in a mysql query. The problem with that arrises when you have someone enter Century 21 and then Century 21 Great Realty, which are two seperate companies...

Any suggestions on dealing with these kinds of variations on user input?

Thanks
-emrys

[mrhappiness]

mysql: SOUNDEX

or

php: [man]similar_text[/man] (for example)