<html>
<head>
<title>multiple file upload </title>
<script type="text/javascript">
function add_file_field(){
var container=document.getElementById('file_container');
var file_field=document.createElement('input');
file_field.name='images[]';
file_field.type='file';
container.appendChild(file_field);
var br_field=document.createElement('br');
container.appendChild(br_field);
}
</script>
</head>
<body>
<form action="mupload.php" method="post" enctype="multipart/form-data" name="mutiple_file_upload_form" id="mutiple_file_upload_form">
<h3>Multiple File Upload </h3>
<div id="file_container"> <input name="images[]" type="file" /> <br /> </div>
<a href="javascript:void(0);" onclick="add_file_field();">Add another</a><br />
<input type="submit" name="Submit" value="Submit" />
</form>
</body>
</html>
This was taken from http://wintekweb.blogspot.com/2012/05/multiple-file-upload-php.html you better to visit it