如何将javascript数据转换为Php值

我想将javascript上的数据转换为php值，我的脚本代码是这样的:

<script type="text/javascript">
$(document).on("click", ".open-image", function (e) {
e.preventDefault();
var _self = $(this);
var image = _self.data('img');
$("#img").val(image);
$("#img").attr('src',image);

$(_self.attr('href')).modal('show');
});
</script>

你可以看到，那里的数据是我在模态上显示的img，这是代码:

<div class="modal fade" id="openimage" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">
  <div class="modal-dialog">
            <div class="modal-content">
                <div class="modal-header">
                    <button type="button" class="close" data-dismiss="modal" aria-hidden="true">&times;</button>
                    <h4 class="modal-title"><i class="fa fa-envelope-o"></i> View Image</h4>
                </div>
                <form action="#" method="post">
                    <div class="modal-body">
                        <center><td width="50" align="center"><img align="center" src="img" id="img" value="img" class="img-rounded" width="200" height="200"></td> 

                    </div>
                    <div class="modal-footer clearfix">
                        <button type="button" class="btn btn-danger" data-dismiss="modal"><i class="fa fa-times"></i> Discard</button>
                        <button type="submit" class="btn btn-primary pull-left"><i class="fa fa-envelope"></i> Send Message</button>
                    </div>
                </form>
            </div><!-- /.modal-content -->
        </div><!-- /.modal-dialog -->

我要做的是将img转换为php值所以我要回显它，正如你在modal上看到的，我这样编码:

<img align="center" src="img" id="img" value="img" class="img-rounded" width="200" height="200">

我想把它转换成php值，比如$img，然后像这样

<img align="center" src="<?php echo $img; ?>" id="img" value="img" class="img-rounded" width="200" height="200">

我该怎么做?