直接看代码吧，很好明白的

复制代码 代码如下:

//用法 echo remote_filesize($url,$user='',$pw='');

$url = "http://www.aa.com/librarys/images/random/rand_11.jpg";//这里要换成你的图片地址

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';

}

函数的思路是，先CURL获取图片到缓冲区，然后正则获取图片的Content-Length信息就OK了。