Php instance for obtaining the volume of remote images

Sometimes, we need to know the size of the remote image. how can PHP do this? Let's look at the code. it's easy to understand.
The code is as follows:
// Use echo remote_filesize ($ url, $ user = '', $ pw = '');
$ Url = "http://www.aa.com/librarys/images/random/rand_11.jpg"; // here you want to change to your image address
Echo remote_filesize ($ url, $ user = '', $ pw = '');

Function remote_filesize ($ uri, $ user = '', $ pw = '')
{
// Start output buffering
Ob_start ();
// Initialize curl with given uri
$ Ch = curl_init ($ uri); // make sure we get the header
Curl_setopt ($ ch, CURLOPT_HEADER, 1); // make it a http HEAD request
Curl_setopt ($ ch, CURLOPT_NOBODY, 1); // if auth is needed, do it here
If (! Empty ($ user )&&! Empty ($ pw ))
{
$ Headers = array ('authorization: Basic '. base64_encode ($ user.': '. $ pw ));
Curl_setopt ($ ch, CURLOPT_HTTPHEADER, $ headers );
}
$ Okay = curl_exec ($ ch );
Curl_close ($ ch); // get the output buffer
$ Head = ob_get_contents (); // clean the output buffer and return to previous // buffer settings
Ob_end_clean (); // gets you the numeric value from the Content-Length // field in the http header
$ Regex = '/Content-Length: \ s ([0-9]. + ?) \ S /';
$ Count = preg_match ($ regex, $ head, $ matches); // if there was a Content-Length field, its value // will now be in $ matches [1]
If (isset ($ matches [1])
{
$ Size = $ matches [1];
}
Else
{
$ Size = 'unknown ';
}
$ Last_mb = round ($ size/(1024*1024), 3 );
$ Last_kb = round ($ size/1024,3 );
Return $ last_kb. 'kb/'. $ last_mb. 'mb ';
}

The idea of the function is to first obtain the image to the buffer using CURL, and then obtain the Content-Length information of the image through regular expression.