How to get the input elements by basing on the formid?

[rizz]

Hi, may i have some idea please on how would i get input elements by just basing on form id?

In my example there are 2 forms with different form name and form id. The first one, form name and id is formm1. Second is form2. My problem is how would i get the length of dtlid[] in form1 and form2?
So basically when i click submit form1 or form 2 i will get the length of form1 dtlid[] so i would know which qty textfields has a value. Any idea please, how it is done?

<div>
<form method="post" name="formm1" id="formm1" action="#">
        <input type="hidden" name="mainid" value="M01">
	<input type="hidden" name="dtlid[]" value="23"><input type="text" name="qty[]">
	<input type="hidden" name="dtlid[]" value="30"><input type="text" name="qty[]">
	<input type="hidden" name="dtlid[]" value="31"><input type="text" name="qty[]">
	<input type="submit" name="submit" value="submit">
</form>
</div>

<div>
<form method="post" name="formm1" id="formm2" action="#">
        <input type="hidden" name="mainid" value="M01">
	<input type="hidden" name="dtlid[]" value="60"><input type="text" name="qty[]">
	<input type="submit" name="submit" value="submit">
</form>
</div>

i have purpose why it is in a different forms. Basically the form is dynamic, it is dependent on the database

[greatstar00]

in each form, have an extra input field
like this
<input type="hidden" name="form_name" value="formm1" />
so, u would know which form is being submitted

[alanphp]

hidden inputs are bad.
javascript can change the values.