If you need both to be request from the browser, using POST, you can use AJAX.

<form onsubmit="handleSubmit()">

</form>

<script type="text/javascript">
function handleSubmit(e) {
    e.preventDefault();
    // then two ajax request
    // may be you can use jQUery
}
</script>

If you just need to execute both files, include or require is your choice.