Checkboxes values

I'm trying to get the values of the checkboxes I check and put them in a php variable, but when I output that value, it gives me zeroes (0). If I check 3 boxes, I get three zeroes, etc. Info: I want every checkbox that is checked, so if cb1 and cb3 are checked, I want the variable to be "cb1cb3"

HTML code:

<div class="form-label-group">
  <h2 for="checkboxes">
    Some text
  </h2>
  <input type="checkbox" id="cb1" onclick="click()" name="cb[]" value="cb1"><label for="cb1">cb1</label><br>
  <input type="checkbox" id="cb2" onclick="click()"  name="cb[]" value="cb2"><label for="cb2">cb2</label><br>
  <input type="checkbox" id="cb3" onclick="click()"  name="cb[]" value="cb3"><label for="cb3">cb3</label><br>
</div>

JS/php code:

function click(){
    
    $("input[name='cb[]']:checked").each(function ()
    {   
        cb+=$(this).text();
        //also tried to put a $ sign in front of the cb variable: $cb+=$(this).text();
        //and with val instead of text: $cb+=$(this).val();
        i++;
    });
}

Hope you can help out