app2/callback.php

<?php
  ##回调方法

$img_url = $_GET['img_url'];

// 返回数据给回调页面

//echo "
//<script>window.parent.document.getElementById('cover_img_url').value='{$img_url}';</script>
//";
echo"
<script src='test7.js' type='text/javascript'></script>
<script>

append_img('{$img_url}');
</script>
";