one of my checkboxes is ignored in post

I have 12 checkboxes mapcheck 1 to 12. But number 7 is always ignored. The CheckBoxes are Generated using Blade.

                @for ($i = 1; $i < 13; $i++)
            <div class="hvr-grow map" >
                <img  id="map"  src="../img/overwatch/maps/map.jpg">
            </div>
            <input name="mapcheck" type="checkbox"  id="mapcheck" value="" style="display:none"/>

            @endfor

the post code:

 for ($i=1; $i < 13; $i++) {

            if($_POST["mapcheck". $i] != null){
                array_push($maps, $i);
            }

    }