<script>
  $(function(){
    $('#main input:checkbox').on("change", function(){
         var summ = '<?php $allsum?>';
        $('#main input:checkbox:checked').each(function(index, element){
            var add = parseInt($(element).val(), 10); 
            if(!isNaN(add))
                summ -= -add;
        });
        $("#result em").text(summ);
    })   
})
</script>

........
var summ = <?=$allsum?>;
$("#result em").text(<?=$allsum?>);