php 获取远程文件的大小

php 获取远程文件的大小 比如：// 实例测试
echo remote_filesize("http://www.heimaolianmeng.com/luoyue/images/logo3.jpg"); 浏览器显示就是16699 字节
下面是源码：
// 获取远程文件的大小
function remote_filesize($url, $user = "", $pw = "")
{
ob_start();
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_HEADER, 1);
curl_setopt($ch, CURLOPT_NOBODY, 1);

if(!empty($user) && !empty($pw))
{
$headers = array('Authorization: Basic ' . base64_encode("$user:$pw"));
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
}

$ok = curl_exec($ch);
curl_close($ch);
$head = ob_get_contents();
ob_end_clean();

$regex = '/Content-Length:\s([0-9].+?)\s/';
$count = preg_match($regex, $head, $matches);

return isset($matches[1]) ? $matches[1] . " 字节" : "unknown";
}

// 实例测试
echo remote_filesize("http://www.heimaolianmeng.com/luoyue/images/logo3.jpg");

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