Warning: require(/var/www/html/vendor/autoload.php): failed to open stream: No such file or directory in /var/www/html/index.php on line 17

Fatal error: require(): Failed opening required '/var/www/html/vendor/autoload.php' (include_path='.:/usr/local/lib/php') in /var/www/html/index.php on line 17

vendor/autoload.php文件是存在的，但是访问报错说文件找不到？。