使用 file_get_contents 上传文件

问题描述

我意识到我可以很容易地使用 CURL 做到这一点，但我想知道是否可以使用 file_get_contents() 和 http 流上下文将文件上传到远程 Web 服务器，以及如果是这样，如何?

I realise I can do this with CURL very easily, but I was wondering if it was possible to use file_get_contents() with the http stream context to upload a file to a remote web server, and if so, how?

推荐答案

首先，multipart Content-Type 的第一条规则是定义一个边界用作每个部分之间的分隔符(因为顾名思义，它可以有多个部分).边界可以是内容正文中未包含的任何字符串.我通常会使用时间戳:

First of all, the first rule of multipart Content-Type is to define a boundary that will be used as a delimiter between each part (because as the name says, it can have multiple parts). The boundary can be any string that is not contained in the content body. I will usually use a timestamp:

define('MULTIPART_BOUNDARY', '--------------------------'.microtime(true));

一旦定义了边界，就必须将它与 Content-Type 标头一起发送，以告诉网络服务器期望的分隔符:

Once your boundary is defined, you must send it with the Content-Type header to tell the webserver what delimiter to expect:

$header = 'Content-Type: multipart/form-data; boundary='.MULTIPART_BOUNDARY;

完成后，您必须构建与 HTTP 规范和您发送的标头相匹配的适当内容正文.如您所知，从表单发布文件时，您通常会有一个表单字段名称.我们将定义它:

Once that is done, you must build a proper content body that matches the HTTP specification and the header you sent. As you know, when POSTing a file from a form, you will usually have a form field name. We'll define it:

// equivalent to <input type="file" name="uploaded_file"/>
define('FORM_FIELD', 'uploaded_file'); 

然后我们构建内容主体:

Then we build the content body:

$filename = "/path/to/uploaded/file.zip";
$file_contents = file_get_contents($filename);    

$content =  "--".MULTIPART_BOUNDARY."
".
            "Content-Disposition: form-data; name="".FORM_FIELD.""; filename="".basename($filename).""
".
            "Content-Type: application/zip

".
            $file_contents."
";

// add some POST fields to the request too: $_POST['foo'] = 'bar'
$content .= "--".MULTIPART_BOUNDARY."
".
            "Content-Disposition: form-data; name="foo"

".
            "bar
";

// signal end of request (note the trailing "--")
$content .= "--".MULTIPART_BOUNDARY."--
";

如您所见，我们正在发送带有 form-data 配置的 Content-Disposition 标头以及 name 参数(表单字段名称)和 filename 参数(原始文件名).如果您想正确填充 $_FILES[]['type'] 东西，那么发送带有正确 MIME 类型的 Content-Type 标头也很重要.

As you can see, we're sending the Content-Disposition header with the form-data disposition, along with the name parameter (the form field name) and the filename parameter (the original filename). It is also important to send the Content-Type header with the proper MIME type, if you want to correctly populate the $_FILES[]['type'] thingy.

如果您有多个文件要上传，您只需使用 $content 位重复该过程，当然，每个文件都有不同的 FORM_FIELD.

If you had multiple files to upload, you just repeat the process with the $content bit, with of course, a different FORM_FIELD for each file.

现在，构建上下文:

$context = stream_context_create(array(
    'http' => array(
          'method' => 'POST',
          'header' => $header,
          'content' => $content,
    )
));

并执行:

file_get_contents('http://url/to/upload/handler', false, $context);

注意:在发送二进制文件之前无需对其进行编码.HTTP 可以很好地处理二进制文件.

NOTE: There is no need to encode your binary file before sending it. HTTP can handle binary just fine.

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