How to add classes to each input radios in radioList()

I’m very beginner in yii2 and i’m syntactically confused to add classes in this chtml

<?= $form->field($model, 'customer_sel')->radioList(array('customer' => 'Customer', 'supplier' => 'Supplier', 'excludecustomer' => 'Exclude Customer', 'all' => 'All'))->label('Select Choice'); ?>

I need to add class names of common(same) and different classes to each radio input. That is it look like in html…

 <div class="form-group field-cashbankentry-customer_sel">
<label class="control-label" for="cashbankentry-customer_sel">Select Choice</label>
<input type="hidden" name="CashBankentry[customer_sel]" value=""><div id="cashbankentry-customer_sel"><label><input type="radio" class="inputbox inputindex_1" name="CashBankentry[customer_sel]" value="customer" checked> Custom</label>
<label><input type="radio" class="inputbox inputindex_2 name="CashBankentry[customer_sel]" value="supplier"> Supplier</label>
<label><input type="radio" class="inputbox inputindex_3 name="CashBankentry[customer_sel]" value="excludecustomer"> Exclude Customer</label>
<label><input type="radio" class="inputbox inputindex_4 name="CashBankentry[customer_sel]" value="all"> All</label></div>

i have classes to add [inputbox(common to all)and inputindex_1-4 to each radios] i’m syntactically confused to add array of classes to this. How to add these classes