Striping unwanted characters from string

Hello All, I was wondering if someone could help me with this : I need to strip unwanted characters from a string. My system has a search script to search parts by partnumber. The Database only holds Partnumbers with characters from A to Z and 0 to 9. Alls characters such as blank space, -, _, * , @ , # & , {, } ,[ , ] : , ; '" should be ignored. The problem is that if a customer is looking for partnumber 1234 and he types 123-4 he ain't find anyhting. So I need a function to get a string parameter and return a result string with nothing but 0 to 9 and A to Z. I understarnd PHP has some built in string functions such as Trim() and ltrim() for blank spaces. Has anyone done this before? I would apreciate a few hints. thank you, Carlos Fernando Scheidecker Antunes