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PHP的AJAX技术实现文件异步上传

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Release: 2016-06-08 17:33:14
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异步的文件上传是在现代的AJAX实现的Web应用里面经常要遇到,必须解决的问题。但是标准的AJAX类(XmlHttpRequest)无法实现传输文件的功能。因此,这里讨论的内容就是如何在AJAX的技术的基础之上构建异步的文件上传功能。在这个功能当中需要使用到内置的框及(IFRAME)来传输文件。这个功能实现的效果是页面在上传文件的时候,用户还可以使用该页面并且填写文件描述。

  这个例子是我们引用AJAX的经典案例进行分析的。

  系统环境

  · 较新版本的浏览器。例如Opera,Firefox或者 Internet Explorer。

  · PHP 4.3.0 或更高版本

  · PHP 5 版本

  · PHP 中的 'short_open_tag' 选项开启(否则会发生解析错误)。

  功能分析

  通过内置的IFRAME(框架)进行文件上传。具备包括三个部分组成。

  · 在页面中间有一个简单的<form...表单,表单只包含了<input type="file" ... >控件。这个表单的目标链接就是一个隐藏得IFRAME(通过 CSS的风格" display: none;"实现)并且表单里面唯一一个控件的OnChange事件用来触发JavaScript函数。这个函数的作用是检查用户提交的扩展名,然后提交表单。

  · 在服务器端用PHP编写了一个处理过程(用FILEFRAME坐注释了)。这个处理过程用来把从客户端上传的文件进行检查后保存在服务器,并且通过Javascript代码的形式返回给用户。返回给用户的Javascript脚本通过"parent.window.document"更改了用户现在正在查看的页面,设置了文件的名称并启用了让用户提交表单的按钮。启用按钮的操作是通过getElementById函数实现的。

  · 在主页面还有一个表单,它包含了用户提交的描述和隐藏的文件名。用户可以在文件上传的同时填写文件的描述。当文件上传结束以后,用户点击按钮,就可以看上传以后返回给用户的文件信息了。(通过返回来的文件名和用户输入的描述构成文件信息)。

  可能你会说这么操作不符合常理:文件在用户确认之前就已经被提交了。如果用户没有提交的话,情况会如何呢。你可以自己在扩展处理被用户放弃的文件。

  这个例子把文件存储在一个文件系统的目录下。你需要在脚本开始运行的时候配置下这个目录,具体的包含这个目录信息的变量是$upload_dir 和$web_upload_dir。这里有一个对目录是否可写的权限检查。

  这里我们用到了以下几个PHP函数:

  · move_uploaded_file - 转移一经上传到服务器的文件

  · fopen - 打开文件

  · fwrite - 把内容写入文件

  · fclose - 关闭文件

  · str_replace - 替换字符串

  · filesize - 返回文件大小

  · filemtime - 返回处理时间

  你可以通过手册查到这些函数如果使用。请注意要把HTM(<, >, &)标记替换为(<, > 和 &).


  源代码



<?php
$upload_dir = "/var/www/anyexample/aeu"; // 文件存储的路径
$web_upload_dir = "/aeu"; // 文件在Web目录下的路径
$tf = $upload_dir.'/'.md5(rand()).".test";
$f = @fopen($tf, "w");
if ($f == false)
die("Fatal error! {$upload_dir} is not writable. Set 'chmod 777 {$upload_dir}'
or something like this");
fclose($f);
unlink($tf);

//处理上传的文件
if (isset($_POST['fileframe']))
{
 $result = 'ERROR';
 $result_msg = 'No FILE field found';

 if (isset($_FILES['file'])) // 从浏览器接受文件
 {
  if ($_FILES['file']['error'] == UPLOAD_ERR_OK) // 没有错误
  {
   $filename = $_FILES['file']['name']; // 文件名
   move_uploaded_file($_FILES['file']['tmp_name'], $upload_dir.'/'.$filename);
   // 处理的主过程-转移文件到 $upload_dir
   $result = 'OK';
  }
  elseif ($_FILES['file']['error'] == UPLOAD_ERR_INI_SIZE)
   $result_msg = 'The uploaded file exceeds the upload_max_filesize directive in php.ini';
  else
   $result_msg = 'Unknown error';
 }

 echo '<html><head><title>-</title></head><body>';
 echo '<script language="JavaScript" type="text/javascript">'."\n";
 echo 'var parDoc = window.parent.document;';
 '
 if ($result == 'OK')
 {
  echo 'parDoc.getElementById("upload_status").value = "file successfully uploaded";';
  echo 'parDoc.getElementById("filename").value = "'.$filename.'";';
  echo 'parDoc.getElementById("filenamei").value = "'.$filename.'";';
  echo 'parDoc.getElementById("upload_button").disabled = false;';
 }
 else
 {
  echo 'parDoc.getElementById("upload_status").value = "ERROR: '.$result_msg.'";';
 }

 echo "\n".'</script></body></html>';
 exit();
}

function safehtml($s)
{
 $s=str_replace("&", "&", $s);
 $s=str_replace("<", "<", $s);
 $s=str_replace(">", ">", $s);
 $s=str_replace("'", "'", $s);
 $s=str_replace("\"", """, $s);
 return $s;
}

if (isset($_POST['description']))
{
 $filename = $_POST['filename'];
 $size = filesize($upload_dir.'/'.$filename);
 $date = date('r', filemtime($upload_dir.'/'.$filename));
 $description = safehtml($_POST['description']);

 $html =<<<END
 <html><head><title>{$filename} [uploaded by IFRAME Async file uploader]</title></head>
 <body>
  <h1>{$filename}</h1>
  <p>This is a file information page for your uploaded file. Bookmark it, or send to anyone...</p>
  <p>Date: {$date}</p>
  <p>Size: {$size} bytes</p>
  <p>Description:
  <pre>{$description}</pre>
  </p>
  <p><a href="{$web_upload_dir}/{$filename}" style="font-size: large;">download file</a><br>
  <a href="{$PHP_SELF}" style="font-size: small;">back to file uploading</a><br>
  <a href="{$web_upload_dir}/upload-log.html" style="font-size: small;">upload-log</a></p>
  <br><br>Example by <a href="http://www.anyexample.com/">AnyExample</a>
 </body></html>
 END;
 
 $f = fopen($upload_dir.'/'.$filename.'-desc.html', "w");
 fwrite($f, $html);
 fclose($f);
 $msg = "File {$filename} uploaded,
 <a href='{$web_upload_dir}/{$filename}-desc.html'>see file information page</a>";

 $f = fopen($upload_dir."/upload-log.html", "a");
 fwrite($f, "<p>$msg</p>\n");
 fclose($f);

 setcookie('msg', $msg);
 header("Location: http://".$_SERVER['HTTP_HOST'].$PHP_SELF);
 exit();
}

if (isset($_COOKIE['msg']) && $_COOKIE['msg'] != '')
{
 if (get_magic_quotes_gpc())
  $msg = stripslashes($_COOKIE['msg']);
 else
  $msg = $_COOKIE['msg'];
  setcookie('msg', '');
}
?>
<!-- Beginning of main page -->
<html><head>
<title>IFRAME Async file uploader example</title>
</head>
<body>
<?php
 if (isset($msg))
  echo '<p style="font-weight: bold;">'.$msg.'</p>';
?>
<h1>Upload file:</h1>
<p>File will begin to upload just after selection. </p>
<p>You may write file description, while you file is being uploaded.</p>

<form action="<?=$PHP_SELF?>" target="upload_iframe" method="post" enctype="multipart/form-data">
 <input type="hidden" name="fileframe" value="true">
 <!-- Target of the form is set to hidden iframe -->
 <!-- From will send its post data to fileframe section of this PHP script (see above) -->

 <label for="file">text file uploader:</label><br>
 <!-- JavaScript is called by OnChange attribute -->
 <input type="file" name="file" id="file" onChange="jsUpload(this)">
</form>
<script type="text/javascript">
/* This function is called when user selects file in file dialog */
function jsUpload(upload_field)
{
 // this is just an example of checking file extensions
 // if you do not need extension checking, remove
 // everything down to line
 // upload_field.form.submit();
 
 var re_text = /\.txt|\.xml|\.zip/i;
 var filename = upload_field.value;

 /* Checking file type */
 if (filename.search(re_text) == -1)
 {
  alert("File does not have text(txt, xml, zip) extension");
  upload_field.form.reset();
  return false;
 }

 upload_field.form.submit();
 document.getElementById('upload_status').value = "uploading file...";
 upload_field.disabled = true;
 return true;
}
</script>
<iframe name="upload_iframe" style="width: 400px; height: 100px; display: none;">
</iframe>
<!-- For debugging purposes, it's often useful to remove
"display: none" from attribute -->

<br>
Upload status:<br>
<input type="text" name="upload_status" id="upload_status"
value="not uploaded" size="64" disabled>
<br><br>

File name:<br>
<input type="text" name="filenamei" id="filenamei" value="none" disabled>

<form action="<?=$PHP_SELF?>" method="POST">
 <!-- one field is "disabled" for displaying-only. Other, hidden one is for sending data -->
 <input type="hidden" name="filename" id="filename">
 <br><br>

 <label for="photo">File description:</label><br>
 <textarea rows="5" cols="50" name="description"></textarea>

 <br><br>
 <input type="submit" id="upload_button" value="save file" disabled>
</form>
<br><br>
<a href="<?=$web_upload_dir?>/upload-log.html">upload-log</a>
<br><br><br>

Example by <a href="http://www.anyexample.com/">AnyExample</a>
</body>
</html>

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