Protect your data from user input

I came to a point where I needed to filter the user input (not just tell the user something like : “The username isn’t in the right format” or “Please choose a valid name for your username”), I mean let him to input in the form anything he wanted too but in the end what we store in the database is his processed input (only A-Z, a-z and 0-9).
I had the Visual Basic and C++ thinking .. I must do that and that and that to get rid of unwanted characters. It was a little time consuming and I was in hurry so I googled and I reached the ereg_replace help page on PHP.net website. Suddenly all became much much easier , just write a regular expression (ohh, by the way .. if someone asks I can write a small tutorial on regular expressions) like this : “[^A-Za-z0-9]” and that was it .

Below is a small example on how to filter (remove all characters except uppercase/lowercase letters and numbers)

PHP is a strong language with a lot of functions that help us to decrease the development time. So before thinking how to do a certain thing just take a look first at www.php.net and see if what you need isn’t already done