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In PHP, handling file downloads often involves the need for file resumption. This feature allows users to resume downloading from the point where the download was interrupted, avoiding the need to download the entire file again. The key to achieving file resumption usually lies in managing HTTP headers and the server's support for Range requests.
So, can stream_context_set_params be used for file resumption? How should it be configured?
stream_context_set_params is a PHP function used to set parameters for an existing stream context. It's commonly used to adjust the behavior of streams, such as timeouts, notification callbacks, and more. The usage syntax is as follows:
stream_context_set_params(resource $stream_context, array $params): bool
The parameters can include:
notification: Sets a callback function
timeout: Sets the timeout duration (in seconds)
blocking: Whether to block the stream
The implementation of file resumption mainly relies on the Range header in the HTTP protocol. The server responds by returning the corresponding byte range of the file based on the request header. For example:
Range: bytes=1000-
This means the client wants to resume downloading from byte 1000.
When the server receives such a request, it responds with the status code 206 Partial Content and includes the Content-Range header in the response, indicating which part of the file has been returned.
Strictly speaking, stream_context_set_params is not designed to handle HTTP headers. It is used for setting parameters for streams, so it cannot directly configure the Range header in HTTP requests or handle the server's response status codes and segmented transfer.
If you want to initiate an HTTP request supporting file resumption in PHP, you should use stream_context_create together with HTTP options to set the request header, such as:
$options = [
'http' => [
'method' => 'GET',
'header' => "Range: bytes=1000-\r\n",
]
];
$context = stream_context_create($options);
$file = file_get_contents('http://m66.net/path/to/file', false, $context);
This way, the client can request the file to start downloading from the specified byte position.
<?php
$start = 1000; // Start downloading from byte 1000
<p>$options = [<br>
'http' => [<br>
'method' => 'GET',<br>
'header' => "Range: bytes=$start-\r\n",<br>
'ignore_errors' => true, // Allow 206 response<br>
]<br>
];</p>
<p>$context = stream_context_create($options);</p>
<p>$url = '<a rel="noopener" target="_new" class="" href="http://m66.net/path/to/largefile.zip">http://m66.net/path/to/largefile.zip</a>';</p>
<p>$fileContent = file_get_contents($url, false, $context);</p>
<p>// Append $fileContent to an existing file to implement resumption<br>
file_put_contents('localfile.zip', $fileContent, FILE_APPEND);</p>
<p>?><br>
In the example above, the key is adding the Range header in the http options, so the server returns a partial file. stream_context_set_params was not used, as it does not handle setting request headers.
Initiating a request with the Range header from the client is just the first step. The server must correctly support and respond to requests with the Range header.
The server must return the status code 206 Partial Content
The server must correctly set the Content-Range header
The server must support partial file reading
If the server does not support these, the client’s request with the Range header will still return the entire file.
stream_context_set_params is mainly used to set stream parameters and is not used to set HTTP request headers, so it cannot directly implement file resumption.
To implement file resumption, use stream_context_create and set the Range request header in the http options.
File resumption requires the server to correctly support Range requests.
By combining PHP file handling functions, you can achieve client-side file resumption functionality.
