Replacing an ad agency's budget and revenue management with an in-house web system built on Slim + MySQL

What changed

• Monthly aggregation time
  Shortened versus Excel operation
• Input errors
  Structurally curbed by validation
• Business team self-sufficiency
  Engineer involvement minimized

Challenge

At the ad agency, budget and revenue management was scattered across multiple Excel files, and cross-project, cross-department aggregation took a long time. Every month-end management report, someone had to consolidate the Excel files by hand. Aggregation discrepancies arising from input errors and mismatched file versions occurred frequently, undermining the reliability of management decisions. It wasn't enough just to "replace Excel" — we needed to rebuild it into a system the business team could use in daily operation without hesitation.

Approach

1. 01 Through interviews with the business team, organized how budgets and revenue are handled and the aggregation axes
2. 02 Built a lightweight web system with Slim PHP + MySQL
3. 03 Separated the per-project input screen from the department- and period-based aggregation screens in the design
4. 04 Unified the development environment with Docker, ensuring reproducibility from local to production
5. 05 Committed fully to an admin console UI the business team could operate, building a self-sufficient setup that doesn't require asking engineers
6. 06 Planned a phased migration off Excel, switching over without stopping current operations

Key success factors

UI design driven by the business team

We built the screen layout on the premise that the business team — not engineers — would use it daily, enabling self-sufficient operation.

Choosing a lightweight framework

We chose Slim PHP, holding down maintenance cost with a focused feature set and a simple codebase.

Committing to phased migration

Rather than cutting Excel off all at once, we proceeded through phased migration to avoid operational disruption.

Clarifying the aggregation axes in advance

We fixed the three axes — project, department, and period — at the start, keeping aggregation from breaking as features were added.

Solution

We built lightly with Slim PHP + MySQL and migrated off Excel in stages. We set up an admin console that aggregates flexibly across three axes — project, department, and period — so monthly management reports can be generated in a short time. Validation structurally prevents input errors, and post-launch inquiries stayed low.