在 Ubuntu 下运行 Laravel 项目时，遇到如下提示：

Loading composer repositories with package information
Installing dependencies (including require-dev) from lock file
Nothing to install or update
Generating autoload files
Mcrypt PHP extension required.
Script php artisan clear-compiled handling the post-install-cmd event returned with an error

这是由于 PHP 缺少 Mcrypt 扩展的原因，只要根据提示装上，并启用这个模块就可以了。

sudo apt-get install php5-mcrypt

sudo php5enmod mcrypt