无法启动laravel网站

Ive tried setting up a laravel instance many times now on Ubuntu 16.04 system. I have php5.6 and apache2 installed. Installed composer following the instructions on there site and than ran (composer global require "laravel/installer") to install laravel.

I've added (export PATH="~/.composer/vendor/bin:$PATH") to .bashrc and then create new laravel project with laravel new project. to test if it was working I cd into project and ran (php artisan serve) but keep coming up with

PHP Warning:  require(/home/dave/project/bootstrap/../vendor/autoload.php): failed to open stream: No such file or directory in /home/dave/project/bootstrap/autoload.php on line 17
PHP Fatal error:  require(): Failed opening required '/home/dave/project/bootstrap/../vendor/autoload.php' (include_path='.:/usr/share/php') in /home/dave/project/bootstrap/autoload.php on line 17

Can anyone help get me going.

First you need to install mb-string php extension. this extension is build in to libapache2-mod-php5 extension so the following script will work

sudo apt-get install libapache2-mod-php5

if this package is installed then you should check php.ini file and look for mb-string extension and if it has a semicolon before remove it

then you should restart apache

if still it isn't working then you should look for file permissions