PHP and form data validation -

i beginner in php-codeignitor.so dont know question waste guys.

but there easy way validate form data ?

ex.i have table , contain text field "username",there insert button too,whern user clicked on insert add text field.

so how can value(s) in php ? because user can add number of fields there.

$username = $_post("username"); //what retrieve in case ? array ?

also how can handle situation this.

thank you.

if set array in form, array in $_post.

form fields:

<input type='text' name='username[]' /> <input type='text' name='username[]' /> 

php:

$users_array = $_post['username'];