PHP 实现下载文件

1. readfile  函数    https://www.php.net/manual/en/function.readfile.php 参考示例

   <?php
   $file = 'monkey.gif';
   
   if (file_exists($file)) {
       header('Content-Description: File Transfer');
       header('Content-Type: application/octet-stream');
       header('Content-Disposition: attachment; filename="'.basename($file).'"');
       header('Expires: 0');
       header('Cache-Control: must-revalidate');
       header('Pragma: public');
       header('Content-Length: ' . filesize($file));
       readfile($file);
       exit;
   }
   ?>