php上传文件及头像预览

<form id="sc" action="shangchuan.php" target="hidden_frame" method="post" enctype="multipart/form-data">
    <div id="yl" style="margin-left:0px; 144px; height:170px; background-size:144px 170px; background-image:url(images/%E6%B5%B7%E6%8A%A51101.jpg)">
        <input type="file" name="file" style="144px; height:170px; float:left; opacity:0;" width="146" onchange="document.getElementById('sc').submit()"/>
        <img id="pic" style="display:none"/>
    </div>
    <input type="button" value="保存"/>
</form>
<iframe style="display:none;" name="hidden_frame" id="hidden_frame">
</iframe>

</body>
<script type="text/javascript">
//回调函数
function showimg(aa)
{
    var l = document.getElementById("yl");
    var p = document.getElementById("pic");
    
    l.style.backgroundImage = "url("+aa+")";
    p.setAttribute("src",aa);
}
</script>

<?php
   //上传文件限制
   if ((($_FILES["file"]["type"] == "image/gif")|| ($_FILES["file"]["type"] == "image/jpeg")|| ($_FILES["file"]["type"] == "image/pjpeg"))&& ($_FILES["file"]["size"] < 10000000))
  {
      //文件上传是否出错
      if ($_FILES["file"]["error"] > 0)
    {
        echo "上传出错: " . $_FILES["file"]["error"] . "<br />";
    }
      else
    {
        //输出文件信息
        /*echo "文件名: " . $_FILES["file"]["name"] . "<br />";
        echo "类型: " . $_FILES["file"]["type"] . "<br />";
        echo "大小: " . ($_FILES["file"]["size"] / 1024) . " Kb<br />";
        echo "临时路径: " . $_FILES["file"]["tmp_name"] . "<br />";*/
    
    //判断文件是否已存在
    if (file_exists("images/" . $_FILES["file"]["name"]))
      {
          echo "<script language='javascript'>alert('".$_FILES["file"]["name"]."已经存在！')</script>";
           
      }
    else
      {
          //造存储路径
          $filename = "images/" . $_FILES["file"]["name"];
          //移动图片至保存路径，解决中文乱码问题
            move_uploaded_file($_FILES["file"]["tmp_name"],iconv("UTF-8","gb2312",$filename));
          
            echo "该文件存储在了: " . "images/" . $_FILES["file"]["name"];
          echo "<script language='javascript'>parent.showimg('".$filename."')</script>";
      }
    }
  }
  else
  {
      echo "上传失败";
  }

?>