UPDATE:
I'm trying to figure out how to keep all the checkboxes checked even after submitting and reloading the page. Currently, they get reset :/
Below is the form code I am working with:
<form action="" method="post" id="filtre_form">
<h1 class="text-center">Filter</h1>
<div class="col-md-6">
<h4 class="text-center">Columns to Display</h4>
<div class="col-md-6">
<ul>
<li>
<label class="checkbox">
<input type="checkbox" value="model" name="checkbox[]" id="Model"> Model
</label>
</li>
<li>
<label class="checkbox">
<input type="checkbox" value="date_sent" name="checkbox[]" id="Date"> Date Sent
</label>
</li>
<li>
<label class="checkbox">
<input type="checkbox" value="distributor" name="checkbox[]" id="Distributor"> Distributor
</label>
</li>