PHP uses request header information to obtain the remote image size

$fp = fsockopen("www.baidu.com", 80, $errno, $errstr, 30);
if ($fp) {
 //Just set the request to HEAD here.
 $out = "HEAD /img/baidu_sylogo1.gif HTTP/1.1rn";
 $out .= "Host: www.baidu.comrn";
 $out .= "Connection: Closernrn";
 fwrite($fp , $out);
 while (!feof($fp)) {
 $header = fgets($fp);
 if (stripos($header, 'Content-Length') !== false) {
 $size = trim(substr($header, strpos($header, ':') + 1));
 echo $size;
 }
 }
 fclose($fp);
} else {
 echo "$errstr ($errno) ";
}

The same as initiating a GET request, just set the request type GET to HEAD. Just modify the requested host and path to what you need.

Summary: PHP can also use get_headers to obtain header information. After testing this function, it is a GET request. For details, please refer to: php function get_headers is a HEAD request or GET request . In addition, some servers may block HEAD requests. If blocked, you can only use GET requests.

In this way, you can directly use the ready-made function getimagesize to get the size of the image.