Depending on the application, it may be easier to just create a drop-down list. It's up to you to determine which is best for your own need.
Now, there are some PHP scripts out there (they aren't that hard) and I believe suggestions have been posted here before.
Also, dynamicdrive.com has a couple of JavaScript solutions available too. Although, be careful of using JavaScript, because if the user is not using IE, or has the JS disabled, it won't function.