How to append multiple values to a single parameter in html form?

Question

Assuming I have the following form:

<form action="process.php">
<input type="checkbox" name="option1" value="oats"> Oats
<input type="checkbox" name="option2" value="beans"> Beans
<input type="hidden" name="parameter" value="a"/>
<input type="submit" value="Submit"/>
</form>

What would normally happen is after clicking on the URL, the browser redirects to:

process.php?option1=oats&option2=beans&parameter=a

How do I make it such that when the submit is clicked all the checkboxes end up as part of the "parameter", but separated by commas? So in other words it would be:

process.php?parameter=a,oats,beans

Best solution with minimal javascript/jquery/html is best if no html solution.

Answer 1

If you want several values in one parameter, you have to name it like parameter[]

f.e.:

<form action="process.php">
<input type="checkbox" name="parameter[]" value="oats"> Oats
<input type="checkbox" name="parameter[]" value="beans"> Beans
<input type="hidden" name="parameter[]" value="a"/>
<input type="submit" value="Submit"/>
</form>