How to Upload Files Using file_get_contents() with Multipart Content-Type and Boundary?

Uploading Files with file_get_contents()

While cURL offers a straightforward method for file uploads, it's possible to leverage the file_get_contents() function with the http stream context. This approach involves creating a multipart Content-Type request with a defined boundary.

Multipart Content-Type and Boundary:

Multipart Content-Type enables multiple parts in the HTTP request body. A boundary string, distinct from the body content, acts as the delimiter between parts. Here's how to define a boundary:

<code class="php">define('MULTIPART_BOUNDARY', '--------------------------' . microtime(true));</code>

HTTP Header and Content Body:

The Content-Type header specifies the boundary to the web server:

<code class="php">$header = 'Content-Type: multipart/form-data; boundary=' . MULTIPART_BOUNDARY;</code>

Next, build the content body by creating parts for each file and field:

<code class="php">define('FORM_FIELD', 'uploaded_file');

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

$content = "--" . MULTIPART_BOUNDARY . "\r\n" .
            "Content-Disposition: form-data; name=\"" . FORM_FIELD . "\"; filename=\"" . basename($filename) . "\"\r\n" .
            "Content-Type: application/zip\r\n\r\n" .
            $file_contents . "\r\n";</code>

Add additional POST fields as needed:

<code class="php">$content .= "--" . MULTIPART_BOUNDARY . "\r\n" .
            "Content-Disposition: form-data; name=\"foo\"\r\n\r\n" .
            "bar\r\n";</code>

End the request with a trailing boundary:

<code class="php">$content .= "--" . MULTIPART_BOUNDARY . "--\r\n";</code>

Stream Context and Execution:

Create the stream context:

<code class="php">$context = stream_context_create(array(
    'http' => array(
          'method' => 'POST',
          'header' => $header,
          'content' => $content,
    )
));</code>

Finally, execute the upload:

<code class="php">file_get_contents('http://url/to/upload/handler', false, $context);</code>

Note: Do not encode binary files before sending them, as HTTP can handle binary data.

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