php获取远程文件大小就需要用到curl来访问远程文件，然后返回文件大小单位为字节

<?php
// 获取远程文件大小函数
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("https://www.zidongcaiji.com/logo.png");
?>

以上实例输出结果为：

8416 字节