PHP AjaxForm submits image upload and displays image

<?php
$file_upload = "upload/";
$file_allow_ext=&#39;gif|jpg|jpeg|png|gif|zip|rar|ppt|xls|pdf|pptx|xlsx|docx&#39;;
$file_allow_size = 5*1024*1024;
if($_POST[&#39;submit&#39;]=="上传"){
 if(is_uploaded_file($_FILES[&#39;file&#39;][&#39;tmp_name&#39;])){
  $file_name = $_FILES[&#39;file&#39;][&#39;name&#39;];
  $file_error = $_FILES[&#39;file&#39;][&#39;error&#39;];
  $file_type = $_FILES[&#39;file&#39;][&#39;type&#39;];
  $file_tmp_name = $_FILES[&#39;file&#39;][&#39;tmp_name&#39;]; 
  $file_size = $_FILES[&#39;file&#39;][&#39;size&#39;];
  $file_ext = substr($file_name, strrpos($file_name, &#39;.&#39;)+1);
  switch($file_error){
  case 0:
  $data[&#39;status&#39;] = 0;
  $data[&#39;msg&#39;] = "文件上传成功!";  
  break;

  case 1:
  $data[&#39;status&#39;] = 1;
  $data[&#39;msg&#39;] = "文件上传失败，文件大小".$file_size."超过限制,允许上传大小".sizeFormat($file_allow_size)."!";  
  break;

  case 3:
  $data[&#39;status&#39;] = 1;
  $data[&#39;msg&#39;] = "上传失败，文件只有部份上传!";  
  break;

  case 4:
  $data[&#39;status&#39;] = 1;
  $data[&#39;msg&#39;] = "上传失败，文件没有被上传!";  
  break;

  case 5:
  $data[&#39;status&#39;] = 1;
  $data[&#39;msg&#39;] = "文件上传失败，文件大小为0!";  
  break; 
  }
  if(stripos($file_allow_ext,$file_ext)===false){
  $data[&#39;status&#39;] = 1;
  $data[&#39;msg&#39;] = "该文件扩展名不允许上传";  
  }
  if($file_size>$file_allow_size){  
  $data[&#39;status&#39;] = 1;
  $data[&#39;msg&#39;] = "文件大小超过限制,只能上传".sizeFormat($file_allow_size)."的文件!"; 
  } 
  if($data[&#39;status&#39;]==1){
  $data[&#39;status&#39;] = 1;
  $data[&#39;msg&#39;] = $data[&#39;msg&#39;];
  exit(json_encode($data)); 
  }
  if($data[&#39;status&#39;]==0){
  if(file_exists($file_upload)){   
   $file_new_name = date("YmdHis").&#39;_&#39;.rand(10000,99999).&#39;.&#39;.$file_ext;
   $file_save_path = $file_upload.$file_new_name; 
   $data[&#39;status&#39;] = 0;  
   $data[&#39;url&#39;] = $file_save_path;
   move_uploaded_file($file_tmp_name,$file_save_path);
   exit(json_encode($data));    
  }else{
   exit(json_encode($data));
  }  

  }   
 }
}

function sizeFormat($size)
{
 $sizeStr=&#39;&#39;;
 if($size<1024)
 {
  return $size."bytes";
 }
 else if($size<(1024*1024))
 {
  $size=round($size/1024,1);
  return $size."KB";
 }
 else if($size<(1024*1024*1024))
 {
  $size=round($size/(1024*1024),1);
  return $size."MB";
 }
 else
 {
  $size=round($size/(1024*1024*1024),1);
  return $size."GB";
 } 
}



?>

<script type="text/javascript" src="http://lib.sinaapp.com/js/jquery/1.9.1/jquery-1.9.1.min.js"></script>
<script type="text/javascript" src="http://files.cnblogs.com/files/china-li/jquery.form.js"></script>

<form action="dofile.php" method="post" enctype="multipart/form-data" id="upfileimage">
<input type="hidden" name="image[]" />
<label for="file">文件:</label><input type="file" name="file" id="file" />
<input type="submit" name="submit" value="上传" />
</form>

<script type="text/javascript">
$("#upfileimage").submit(function(){
 if($("input[type=file]").val()==""){
  alert("请选择要上传的文件");
  return false;
 }
})
$(function(){
 var options = {  
  type:"POST",
  dataType:"json",
  resetForm:true,
  success:function(o){
   if(o.status==1){
   alert(o.msg);
   }else{
   $("body").append("  <img src=&#39;"+o.url+"&#39; alt=&#39;&#39; width=&#39;100&#39; /><input type=&#39;hidden&#39; name=&#39;image[]&#39; value=&#39;"+o.url+"&#39; />");
   }
  },
  error:function(o){
   alert(o.message);
  }  
 }
 $("#upfileimage").ajaxForm(options).submit(function(){return false;});

})
</script>