How Can I Get the Size of a Remote File Without Downloading It?

Determining Remote File Size

Getting the file size of a remote file without downloading it can be a useful optimization in certain scenarios.

Solution

As mentioned in the responses, using an HTTP HEAD request is a suitable approach for this task. HEAD requests retrieve the HTTP headers associated with a resource, without fetching the actual body.

Implementation

Here's a PHP function that leverages this method:

function get_remote_file_size($url) {
  $curl = curl_init($url);
  curl_setopt($curl, CURLOPT_NOBODY, true);
  curl_setopt($curl, CURLOPT_HEADER, true);
  curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
  curl_setopt($curl, CURLOPT_FOLLOWLOCATION, true);

  $data = curl_exec($curl);
  curl_close($curl);

  if ($data) {
    preg_match("/Content-Length: (\d+)/", $data, $matches);
    $content_length = $matches[1] ?? -1;
    return $content_length;
  }

  return -1;
}

Usage

You can use this function to determine the size of a remote file:

$file_size = get_remote_file_size("http://my_url/my_file.txt");

Note: This method relies on the server honoring the HEAD request and providing the correct Content-Length header.

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