Button如何同时提交切换模态

after i click only the modal is executed but the form is not submitted, what are the possible errors in my code?

<a data-toggle="modal" data-target="#purchaseModal">
    <form action="{{url('accept/invoice')}}" method="post">
        {{csrf_field()}}
        <input type="hidden" name="id" value="{{$in->c_id}}">
        <input type="hidden" name="quantity" value="{{$in->c_quantity}}">
        <button type="submit" class="btn btn-alert  btn-circle">
            <i class="fa fa-check"></i>
        </button>
    </form>
</a>

use javascript and jquery

first add an id to your form e.g:id="myform"

than change submit button type to button: type="submit" => type="button"

finally call java script function with onclick attribute, the code should be like this:

 <form action="{{url('accept/invoice')}}" method="post" id="myform">
    {{csrf_field()}}
     <input type="hidden" name="id" value="{{$in->c_id}}">
     <input type="hidden" name="quantity" value="{{$in->c_quantity}}">


<button type="button" class="btn btn-alert  btn-circle" onclick="my_function();">
    <i class="fa fa-check"></i>
</button>
</form>
<script type="text/javascript">
    function my_function() {
        $("#myModal").modal("toggle");
        $("#myform").submit();
    }
</script>

You can try add id to your form tag e.g.

<form action="{{url('accept/invoice')}}" id="form1" method="post">

Then add the id to your button tag

<button type="submit" class="btn btn-alert  btn-circle" form="form1">
 <i class="fa fa-check"></i>
</button>