How do I show the form based on my checkbox value - php

Question

Based on the user selection I want to show the form elements. Here the user selects class1,class6,engg. How do I bring the all form element in one common form right know I am having different form and form field for class 1,6.
My questions Are:
If user select class1 I have list class1 form?
If User select class2 I have to combine class1 and class6 under one form.
Like wise user select class1,class2,class6,engg.
I want to make all the form elments under one form.
My FORM
<form name="frm" method="post">
<table align="center">
<tr>
<td>Name</td>
<td><input type="text" name="txt" id="txt" required ></td><td></td>
</tr>
<tr>
<td>Product</td>
<td>
<input type="checkbox" name="chk[]" value="class1">class1
<input type="checkbox" name="chk[]" value="class6">class6
<input type="checkbox" name="chk[]" value="class8">class8
<input type="checkbox" name="chk[]" value="class10">class10
<input type="checkbox" name="chk[]" value="class12">class12
<input type="checkbox" name="chk[]" value="engineering">engineering
<input type="checkbox" name="chk[]" value="technology">technology
</td><td></td>
</tr>
<tr>
<td></td>
<td><input type="submit" name="submit" value="Save"></td><td></td>
</tr>
</table>
</form>
My PHP VALUES
<?php
if (isset($_POST['submit']))
{
$name = $_POST['txt'];
$product = $_POST['chk'];
print_r($product);
foreach($product as $k=> $v)
{
if($v=="class1")
{
?>
<form name="f1" action="" method="post">
<p>class1
<input type="checkbox" name="chk[]" value="allsubject">allsubject
<input type="checkbox" name="chk[]" value="science">science
<input type="checkbox" name="chk[]" value="maths">maths
</p>
<input type="submit" name="submit" value="submit">
</form>
<?php
}
if($v=="class1" && $v="class6")
{
?>
<form name="f1" action="" method="post">
<p>class1</p>
<input type="checkbox" name="chk[]" value="allsubject">allsubject
<input type="checkbox" name="chk[]" value="science">science
<input type="checkbox" name="chk[]" value="maths">maths
<p>class6</p>
<input type="checkbox" name="chk[]" value="allsubject">allsubject
<input type="checkbox" name="chk[]" value="science">science
<input type="checkbox" name="chk[]" value="maths">maths
<input type="text" name="name" value="">Tutor Name
<input type="text" name="name" value="">Tutor Address
<input type="submit" name="submit" value="submit">
</form>
<?php
}
}
}
?>
I want output like this:
For class1 form:
<form name="f1" action="" method="post">
<p>class1
<input type="checkbox" name="chk[]" value="allsubject">allsubject
<input type="checkbox" name="chk[]" value="science">science
<input type="checkbox" name="chk[]" value="maths">maths
</p>
<input type="submit" name="submit" value="submit">
</form>
For class1, class6 form:
<form name="f1" action="" method="post">
<p>class1</p>
<input type="checkbox" name="chk[]" value="allsubject">allsubject
<input type="checkbox" name="chk[]" value="science">science
<input type="checkbox" name="chk[]" value="maths">maths
<p>class6</p>
<input type="checkbox" name="chk[]" value="allsubject">allsubject
<input type="checkbox" name="chk[]" value="science">science
<input type="checkbox" name="chk[]" value="maths">maths
<input type="text" name="name" value="">Tutor Name
<input type="text" name="name" value="">Tutor Address
<input type="submit" name="submit" value="submit">
</form>