Multiple laravel project on the same hosting

Hi all,

I have four laravel project on the same hosting. Every a few hours the sites don't work and I get error 500. When I get error I get into the settings and just go to the php settings and refresh php and everthing works just fine...

I use version of php 5.6 Laravel project use version: 5.1,5.4.

I enabled json, mcrypt, also set in composer.json to use version of php 5.6.

I check the server errors logs

1. PHP Fatal error: Call to undefined function Illuminate\Foundation\Bootstrap\mb_internal_encoding() in ... 2) PHP Fatal error: Uncaught ReflectionException: Class log does not exist in ... 3) HP Fatal error: Interface 'JsonSerializable' not found in ...

What else can I do?

I don't want to every day refresh php...