composer autoload.php无法打开流：没有这样的文件或目录

I am having problem with this error, I don't have Idea how to fix this.

Warning: require_once(DIR/composer/autoload_real.php) [function.require-once]: failed to open stream: No such file or directory in /home/a2946484/public_html/vendor/autoload.php on line 5

what does it mean ?

Here is my autoload.php

// autoload.php @generated by Composer

require_once __DIR__ . '/composer' . '/autoload_real.php';

return ComposerAutoloaderInitad1b46addec8855e522daae36df0556f::getLoader();

Thank you in advance.

I would suggest deleting the 'vendor' folder of your project and creating it again by running 'composer install' in your project folder in command line.