Upgrade custom CodeIgniter web system to latest PHP version

I need an experienced CodeIgniter developer to help to upgrade a complex custom web-based system from PHP 5.6 to PHP7.1 (minimum) but preferably latest PHP version.

Because the installation of CodeIngniter has been customised many times over several years, we cannot simply upgrade CodeIgniter - this would need someone to go through the core CI functionality and upgrade all scripts to work with the latest version of PHP.

The web system is hosted on a LINUX server, running Cpanel. You'd have cpanel access and access to the database for the development / test site - so no concern about the website being live.

This is also urgent and would need to be completed within the next few days. I need someone who will communicate regularly, keep me updated on progress and agree timelines for contact.

Once this has been completed, we then have another similar project to upgrade a similar (but slightly newer system). This will then help us update around 50 websites which all need updating.

Thank you.