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PHP文件上传实现代码详解

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Jun 20, 2016 pm 01:05 PM

File Upload

PHP文件上传实现代码详解

上传文件功能由两个部分组成，HTML页面和PHP处理部分。

HTML页面主要是让用户选择所要上传的文件，php部分让我们可以把文件存储到服务器的指定目录。

一．HTML部分upload.html

<p><html>   </p><p> <head>        <meta content="text/html; charset=utf-8" http-equiv="Content-Type">    </head>    </p><p><body>        上传Demo：        </p><p><form action="upload.php" method="post" enctype="multipart/form-data">            </p><p><input type="file" name="img" />            </p><p><input type="submit" name="submit" value="上传" />        </p><p></form>    </p><p></body></p><p></html></p>

说明：
1.Input标签中type="file"，表明把输入作为文件来处理。

2.Enctype规定了在提交这个表单时要使用哪种内容类型。在表单需要二进制数据时，比如文件内容，请使用"multipart/form-data"，如果要上传文件，这个属性是必要的。

二．php部分upload.php

<p><?php</p><p>$DST_DIR = '/data/upload/';if ($_FILES['img']['name'] != '') {    </p><p>if ($_FILES['img']['error'] > 0) {</p><p>        echo "上传失败";</p><p> }    else { </p><p>       if (move_uploaded_file($_FILES['img']['tmp_name'], $DST_DIR.$_FILES['img']['name'])) {</p><p>            echo "上传成功"; </p><p>       }   else {  </p><p>          echo "上传失败"; </p><p>       }    }}else {</p><p>    echo "请上传文件";</p><p>}</p>

PHP文件上传实现代码说明：

1. 全局变量$_FILE

此数组包含有所有上传的文件信息。
以我们假设文件上传字段的名称如上例所示，为 img。则
$_FILES['img']['name']
客户端上传的文件的原名称。
$_FILES['img']['type']
文件的 MIME 类型，如果浏览器提供此信息的话。一个例子是“image/gif”。不过此 MIME 类型在 PHP 端并不检查，因此不要想当然认为有这个值。$_FILES['img']['size']：已上传文件的大小，单位为字节。
$_FILES['img']['size']
已上传文件的大小，单位为字节。
$_FILES['img']['tmp_name']
文件被上传后在服务端储存的临时文件名。
$_FILES['img']['error']
和该文件上传相关的错误代码。

2. 关于错误码

$_FILES['img']['error']有以下几种类型
UPLOAD_ERR_OK
其值为 0，没有错误发生，文件上传成功。
UPLOAD_ERR_INI_SIZE
其值为 1，上传的文件超过了 php.ini 中 upload_max_filesize选项限制的值。
UPLOAD_ERR_FORM_SIZE
其值为 2，上传文件的大小超过了 HTML 表单中 MAX_FILE_SIZE 选项指定的值。
UPLOAD_ERR_PARTIAL
其值为 3，文件只有部分被上传。
UPLOAD_ERR_NO_FILE
其值为 4，没有文件被上传。
UPLOAD_ERR_NO_TMP_DIR
其值为 6，找不到临时文件夹。PHP 4.3.10 和 PHP 5.0.3 引进。
UPLOAD_ERR_CANT_WRITE
其值为 7，文件写入失败。PHP 5.1.0 引进。

3.move_uploaded_file
文件被上传后，默认地会被储存到服务端的默认临时目录中（除非 php.ini 中的 upload_tmp_dir设置为其它的路径），文件名是随机的。如果该文件没有被移动到其它地方也没有被改名，则该文件将在表单请求结束时被删除。因此需要通过move_uploaded_file移动临时文件。

经实验copy也能完成move_uploaded_file的功能，为啥要用move_uploaded_file呢？

有说法是move_uploaded_file会对上传文件做一些检查，防止copy引起的一些安全漏洞。但具体copy会带来什么问题呢？
Anyway，既然php给了特定的函数，必然有一定道理，先这么用吧。

三．PHP文件上传安全检查

可以考虑通过$_FILES['img']['size']和$_FILES['img']['type']对上传的文件做一些安全检查，比如限定上传类型，上传文件的大小等。

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