PHP获取图片体积的函数，基本准确

      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'; } 
				$last=round($size/(1024*1024),3); 
				return $last.' MB';
				}
				//用法 echo remote_filesize($url,$user='',$pw='');