Enhance Perfex CRM - Warehouse Management System

We are looking for an experienced PHP / CodeIgniter / Perfex CRM developer to customize and extend our existing Warehouse Management System (WMS).

This is NOT a new website or a system to build from scratch. We already have a working system based on Perfex CRM / CodeIgniter with existing customers, warehouse data, booking processes, Gate-In, tasks, inventory-related modules, and custom functionality.

We need a developer who can first understand the existing codebase and database and then safely develop additional logistics/WMS functionality.

Main development requirements
Customer → Supplier → PO mapping
Supplier Master with GST, address and contact information
PO Master
PO Required / Non-PO customer conditions
Booking Request (BR) improvements
E-Way Bill, Invoice, Delivery Challan and Docket details
Expected Box Quantity / Actual Box Quantity
Expected Weight / Actual Weight
Gate-In PO/document matching
Inward Task workflow
Physical cargo verification
Unloading process
Box-wise inventory
Box-wise quantity and weight
Length × Breadth × Height dimensions
Volumetric weight
Warehouse / Rack / Location management
Damage quantity and damage reporting
Repacking
Packing List
Sticker integration
Outbound / Delivery Order
Inventory and stock reports
Periodic physical inventory verification
Role/permission-based visibility for Rate and Amount
Important weight calculation

The system must maintain:

Actual Weight
Volumetric Weight
Chargeable Weight

Chargeable Weight must always use the higher value.

Example:

Actual Weight = 40 KG
Volumetric Weight = 3 KG
→ Chargeable Weight = 40 KG

Actual Weight = 40 KG
Volumetric Weight = 55 KG
→ Chargeable Weight = 55 KG

This calculation needs to work at box level and aggregate correctly where required.

Important development condition

Our existing system already contains operational data.

The developer must:

Take backups before making changes
NOT delete existing data
NOT disturb currently working modules
Understand existing database relationships before modifying them
Extend existing functionality wherever practical instead of unnecessarily rebuilding everything
Work and test on our staging environment
Document database changes
Provide all source code
No encrypted/obfuscated code
Provide a list of modified files
Test the complete workflow before handover
Skills required

We prefer someone with strong experience in:

PHP, CodeIgniter, MySQL, Perfex CRM customization, JavaScript/AJAX, Warehouse Management Systems, Inventory Management, Logistics/ERP workflows, database design and debugging existing systems.

Experience with Perfex CRM modules/custom development is highly preferred.

When applying, please answer:
Have you customized Perfex CRM before?
Have you developed a WMS, inventory, logistics, inward/outward or ERP system?
Please share 2-3 similar projects.
How many years of PHP/CodeIgniter experience do you have?
Are you comfortable working with an existing customized codebase instead of rebuilding it?
How will you ensure our existing data is not affected?
Can you work phase-by-phase on a staging server?
What is your estimated timeline after reviewing the existing system?
Are you personally doing the development, or will it be outsourced to another developer?

Please do not apply if your experience is mainly WordPress/web design. We need an experienced backend developer who understands database-driven WMS/ERP workflows.