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("//www.jb51.net/images/logo.gif")
?>