I'm crating a plugin option page from the code below. However, it does not explain how to get validation on the input fields.
How do I get validation on
id_number for NUMBER ONLY?
Also, can I add default value to the input? on
<input type="text" id="title" name="my_option_name[title]" value="%s" />'
So first time install plugin, it will say something instead of nothing.