php获取远程图片体积大小

实测可用，基本准确，进行了一小部分修改，返回的是字节。

/*
//用法 echo remote_filesize($url,$user='',$pw='');
获取远程图片的尺寸大小
 */
function remote_filesize($uri, $user='', $pw=''){ 
    // start output buffering 
    ob_start();
    // initialize curl with given uri 
    // make sure we get the header
    $ch = curl_init($uri); 
    // make it a http HEAD request 
    curl_setopt($ch, CURLOPT_HEADER, 1); 
    // if auth is needed, do it here 
    curl_setopt($ch, CURLOPT_NOBODY, 1); 
    if (!empty($user) && !empty($pw)) {
        $headers = array('Authorization: Basic ' . base64_encode($user.':'.$pw)); 
        curl_setopt($ch, CURLOPT_HTTPHEADER, $headers); 
    }
    $okay = curl_exec($ch); 
    // get the output buffer 
    curl_close($ch); 
    // clean the output buffer and return to previous // buffer settings 
    $head = ob_get_contents(); 
    ob_end_clean();  
    // gets you the numeric value from the Content-Length // field in the http header
    $regex = '/Content-Length:\s([0-9].+?)\s/'; 
    // if there was a Content-Length field, its value
    $count = preg_match($regex, $head, $matches);   
    // will now be in $matches[1] 
    if (isset($matches[1])) { 
        $size = $matches[1]; 
    } else { 
        $size = 0;
    } 
    // $last=round($size/(1024*1024),3); 
    // return $last.' MB';
    return $size;
}

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。