How do I validate non-required fields?

[eluser]sv3tli0[/eluser]
@Skyscraper:

If you are at user settings page and you are updating user fields and there is last_name your script should update it.

Not to change it just set the old value inside the last name input and it will update it self..
So if user change it to empty your check will said : "at least 4 symbols.."
And if user doesn't change it the old value will update it self with the same value.. And you will keep it as it is!


Your case is custom "Don't update field if its empty"..
Perhaps you must create dependence on which to update your table..