if we need some fields from different tables
temporarily in our software or application then

when you submit form with input and select
controls,the values of these controls are
passed with form.we get these as POST var-
$_POST["controlname"];

session is a essential part of joomla. It's main use
is for remembering user login, also there are many
usage of it.

Today ajax is being a common part in most large website and
application.user loves the way everything done without page
refresh and website's with ajax implemented is getting higher
popularity.in the following i showed how to use ajax in asp.net
web page.you can use in php too -

the following codes show how to create dynamic
check boxes according to database data.also the
tricky part is that whether a check box will
be checked or not can be done by the code '$checked'.