ajax(iframe)无刷新提交表单、上传文件

!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
html xmlns="http://www.w3.org/1999/xhtml">
head>
meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
title>无刷新提交表单/title>
script type="text/javascript">
!--
function callback(str){
alert(str);
}

// -->/script>
/head>
body>
form name="form1" method="POST" action="../post.php" target="post_frame" enctype="multipart/form-data">
iframe name='post_frame' id="post_frame" style="display:none;" mce_style="display:none;">/iframe>
input type="file" name="img" />
input name="power[]" type="text"/>
input type="submit" value="完成以上修改" name="submit" />
/form>
/body>
/html>

echo ("script type=\"text/javascript\">parent.callback('操作成功 ! ')/ script>");