PHP Upgrade for Codeignitor Billing System

I need a developer who knows codeigniter (not sure which version) who can upgrade billing system from php 7.4 to php 8.2 - that it. Can you do this?

If you cost too much i will buy another billing system if its not worth it.
Otherwise if you can fix quickly i will proceed with project.

Summary:
I have this software been using for long time
https://codecanyon.net/item/ibilling-crm-accounting-and-billing-software/11021678

only compatible with php 7.4 and my server deprecated this version and i need to upgrade system to php 8.2

I edit the htaccess file to php 7.4 and system is working. Only issue is it will NOT send email invoice.

This is the error
Whoops\Exception\ErrorException thrown with message "Trying to access array offset on value of type int"

Stacktrace:
#9 Whoops\Exception\ErrorException in /home2/superlu/public_html/billing/vendor/mpdf/mpdf/src/Mpdf.php:21496
#8 Whoops\Run:handleError in /home2/superlu/public_html/billing/vendor/mpdf/mpdf/src/Mpdf.php:21496
#7 Mpdf\Mpdf:_fixTableBorders in /home2/superlu/public_html/billing/vendor/mpdf/mpdf/src/Tag/Table.php:648
#6 Mpdf\Tag\Table:close in /home2/superlu/public_html/billing/vendor/mpdf/mpdf/src/Tag.php:250
#5 Mpdf\Tag:CloseTag in /home2/superlu/public_html/billing/vendor/mpdf/mpdf/src/Mpdf.php:13540
#4 Mpdf\Mpdf:WriteHTML in /home2/superlu/public_html/billing/application/models/Invoice.php:202
#3 Invoice:pdf in /home2/superlu/public_html/billing/application/controllers/invoices.php:1761
#2 include in /home2/superlu/public_html/billing/application/helpers/ibilling_bootstrap.php:373
#1 require in /home2/superlu/public_html/billing/application/app.php:5
#0 require in /home2/superlu/public_html/billing/index.php:24