A simple AJAX download counter. Count is stored in a json file, and updated via PHP.

gistfile1.txt

// jQuery to update counter when button is clicked
$('#download').click(function(event) {
  event.preventDefault();
	var redirectUrl = $(this).attr('href');
	$.ajax({
		url: "downloads.php",
		success: function(response) {
			if (response = 'success') {
				// The counter file has been updated in the background, but we should update the results on screen to tell the user
				var count = $('#count').html();
				$('#count').html(parseFloat(count) + 1);
				
				// Then redirect so that file can download
				window.location.href = redirectUrl;
			}
		}
	});
	return true;
});

// jQuery to get the current count on page load
$.ajax({
	url: "get-downloads.php",
	success: function(data) {
		var data = JSON.stringify(data, null, 4);
		var data = $.parseJSON(data);

		$('#count').html(data.count);
	}
});

// contents of downloads.php
<?php
	$file = "downloads.json";
	$json = json_decode(file_get_contents($file), true);
	$json['count'] = $json['count'] + 1;
	file_put_contents($file, json_encode($json));
	echo 'success';
?>

// contents of get-downloads.php
<?php
	$file = "downloads.json";
	$json = json_decode(file_get_contents($file), true);
	header('Content-Type: application/json');
	echo json_encode($json);
?>

// contents of downloads.json as a starting point
{"count":1}

nice