PHP forms/security

[ktsirig]

Hi all,
I don't know much about security and stuff. I just wanted to know whether I have to take any precautions in a PHP form I have written, from which the user can extract data from my SQL database.
In most fields supplied by the form, users can enter digits and/or text.
Do I need to check/validate anything?
Any hints on how to start or any tutorial suggestions?

Thanx

[sypher]

First off i use basic html validation such as limit a field length etc.

Then i use preg_replace to change any tags such as <input>.
If its for an email address you may also want to validate the domain.

[Pheonix]

Don't trust the html length restrictions, http posts don't have to come from a browser, and browsers don't nessicsarly enforce the rule.