How to solve the problem of not getting the file size when downloading PHP

When using PHP to download files, sometimes you may encounter the problem of not being able to obtain the file size. This problem may occur due to the following reasons:

1. The server does not support obtaining the file size. In some cases, the server may not support obtaining file size information. At this time, when using PHP to download files, the file size will not be obtained.
2. The network environment is unstable. When downloading large files, you often encounter an unstable network environment. At this time, it is entirely possible to make an error in obtaining the file size in PHP.

So how to solve this problem? Here are some solutions for reference:

1. Use CURL to get the file size. You can use the CURL function library to obtain file size information. The code example is as follows:

$url = 'http://example.com/file.zip';
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HEADER, true);
curl_setopt($ch, CURLOPT_NOBODY, true);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
$data = curl_exec($ch);
$fileSize = curl_getinfo($ch, CURLINFO_CONTENT_LENGTH_DOWNLOAD);
curl_close($ch);

2. Directly obtain the server response header to obtain the file size. Use PHP's stream_context_set_default function to set the default http-header and directly obtain the file size information. The sample code is as follows:

$url = 'http://example.com/file.zip';
$opts = array(
  'http' => array(
    'method' => 'HEAD'
  )
);
$context = stream_context_create($opts);
$fp = fopen($url, 'r', false, $context);
$meta = stream_get_meta_data($fp);
foreach ($meta['wrapper_data'] as $value) {
  if (stristr($value, 'content-length')) {
    $content_length = (int) trim(substr($value, 15));
  }
}
fclose($fp);

In summary, it is necessary to solve the problem of PHP not being able to obtain the file size when downloading files. , you can use CURL or get the server response header directly to get the file size. These methods can help PHP developers better manage and control the file download process, improving user experience and application performance.

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