Пошаговая работа скрипта.

loader.php

<div class="loader">Loade...</div>
<div class="step"></div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.2.4/jquery.min.js"></script>

<script type="text/javascript">
    function func(i)
    {
        var form_data = new FormData();
        form_data.append('ITER', i);
        $.ajax({
            type: "POST",
            async: true,
            url: '/hlCoordinateSetter.php',
            cache: false,
            contentType: false,
            processData: false,
            data: form_data,
            beforeSend: function() {
                $('.loader').show();
            },
            success: function(result) {
                console.log(result);
                $('.step').html(result);
                var nextstep = parseInt(result)+1;
                setTimeout(func, 5000, nextstep);
            },
            error: function(error) {
                alert('error; ' + eval(error));
            },
            complete: function() {
                $('.loader').hide();
            }
        });
    }
    var i = 1;
    setTimeout(func, 300, i);
</script>