Having Multiple Modals per page

I'm creating a website where the user can click on an image to open a modal with menu items within, while the first modal works fine, subsequent modals do not.

JS Code:

<script>
// Get the modal
var modal = document.getElementById('myModal');

// Get the button that opens the modal
var btn = document.getElementById("myImg");

// Get the <span> element that closes the modal
var span = document.getElementsByClassName("close")[0];

// When the user clicks the button, open the modal 
btn.onclick = function() {
    modal.style.display = "block";
}

// When the user clicks on <span> (x), close the modal
span.onclick = function() {
    modal.style.display = "none";
}

// When the user clicks anywhere outside of the modal, close it
window.onclick = function(event) {
    if (event.target == modal) {
        modal.style.display = "none";
    }
}
</script>

HTML where its used:

    <div class="col-md-3">
        <h2>Starters</h2>
        <img src="http://ift.tt/2gKaOQN" height="100%" width="100%" id="myImg">
                <!-- The Modal -->
                <div id="myModal" class="modal">

                  <!-- Modal content -->
                  <div class="modal-content">
                    <div class="modal-header">
                      <span class="close">×</span>
                      <br>
                      <h2>Starters</h2>
                    </div>
                    <div class="modal-body">
                      <p><b>PRODUCT <span style="display:inline-block; width: 75%;"></span> PRICE</b></p>
                      <hr>
                      <p> Humus <span style="display:inline-block; width: 78%;"></span>  £3.00</p>
                      <p> Dolma <span style="display:inline-block; width: 78%;"></span>  £3.20</p>
                      <p> Coleslaw <span style="display:inline-block; width: 77%;"></span>  £1.50</p>
                      <p> Prawn Cocktail <span style="display:inline-block; width: 73.5%;"></span>  £4.60</p>
                    </div>

                  </div>

                </div>

    </div>

    <div class="col-md-3">
        <h2>Wraps</h2>
        <img src="http://ift.tt/2gWR0wK" height="100%" width="100%" id="myImg">

                <div id="myModal" class="modal">

                  <!-- Modal content -->
                  <div class="modal-content">
                    <div class="modal-header">
                      <span class="close">×</span>
                      <br>
                      <h2>Starters</h2>
                    </div>
                    <div class="modal-body">
                      <p><b>PRODUCT <span style="display:inline-block; width: 75%;"></span> PRICE</b></p>
                      <hr>
                      <p> Chicken Wrap <span style="display:inline-block; width: 78%;"></span>  £3.00</p>
                      <p> Doner Wrap <span style="display:inline-block; width: 78%;"></span>  £3.20</p>
                      <p> Shish Wrap <span style="display:inline-block; width: 77%;"></span>  £1.50</p>
                      <p> Kofte Wrap <span style="display:inline-block; width: 73.5%;"></span>  £4.60</p>
                    </div>

                  </div>

                </div>

    </div>

The first modal box shown will work as expected, while the second will not show at all, i would rather not have to unnecessarily replicate JavaScript if i don't have to, which is why i tired this method.

Very new to JS and modal boxes, so any input would be appreciated, thanks.