获取远程文件大小的php函数

<?php 
function getFileSize($url){ 
$url = parse_url($url); 
if($fp = @fsockopen($url['host'],empty($url['port'])?80:$url['port'],$error)){ 
fputs($fp,"GET ".(empty($url['path'])?'/':$url['path'])." HTTP/1.1\r\n"); 
fputs($fp,"Host:$url[host]\r\n\r\n"); 
while(!feof($fp)){ 
$tmp = fgets($fp); 
if(trim($tmp) == ''){ 
break; 
}else if(preg_match('/Content-Length:(.*)/si',$tmp,$arr)){ 
return trim($arr[1]); 
} 
} 
return null; 
}else{ 
return null; 
} 
} 
//调用方法
echo getFileSize("http://www.jb51.net/images/logo.gif") 
?>