NewNewbie: Error Checking Forms

[Anon]

I know how to error check if someone leaves a form blank. However, I'm uncertain how to check if the user makes invalid entries. For instance, suppose a user types in an invalid email address by omitting @. Or suppose a user inputs numbers rather than characters into the name field. How can I check for that?

Thanks!

[vsego]

With regular expressions. For e-mail:

if (ereg("^{[@]+@[@]+.[@]+$",} $input))
...good address...
else
...bad address...

This still allows some bad input (i.e. use of spaces), but it can be improved, depending on what exactly you want. Kinda long to explain it all here.

[Anon]

I favor using regular expressions when validating data because of its flexibility, but you could also use php functions such as gettype(), isset(), is_int(), is_long, etc.