From the 4wp.dev team. We build WordPress plugins and write about WordPress engineering. This is how we see SDLC, and the interactive version of this article lives on 4wp.dev: 👉 scroll through sixty years of weather on 4wp.dev/sdlc
SDLC was born in the 1960s. It is still relevant in the AI era.
SDLC (Software Development Life Cycle) is the process every WordPress project goes through, whether you call it that or not: someone wants something, you clarify it, design it, build it, test it, deploy it and maintain it. Many WordPress developers know this process by heart and have never used the letters. Developers say "task", "flow", "release". Managers, tech leads and hiring teams say SDLC.
At 4wp.dev we draw SDLC as an umbrella: the phases are its ribs, and every era of software is new weather. We call it the SDLC Umbrella, and the rest of this article walks under it. This article explains the software development life cycle in a WordPress developer's language.
What Is SDLC?
SDLC stands for Software Development Life Cycle: the phases software goes through from an idea to the day it is switched off. Sources split it into five to eight phases and name them differently. The order stays the same.
The 7 Phases of SDLC (the 7 Ribs of the 4wp.dev Umbrella)
- Plan: why we build it, what it is worth, what the risks are.
- Requirements: what exactly it must do.
- Design: how it will be built.
- Build: the code.
- Test: proof that it works.
- Deploy: getting it live.
- Maintain: keeping it alive, then feeding the next Plan.
SDLC vs Methodologies: Waterfall, Agile, Scrum, Kanban
SDLC is not a methodology. Waterfall, Agile, Scrum and Kanban are different ways of walking through the same phases. SDLC is what they all walk through.
Think of the phases as the ribs of an umbrella. Remove one and the canopy fails:
- Skip Requirements and you build the wrong thing well.
- Skip Design and every new feature fights the old ones.
- Skip Test and your users test for you.
- Skip Maintain and the site slowly rots under plugin, core and PHP updates.
A Short History of SDLC: Sixty Years of Weather
- 1968: the software crisis. At the NATO Software Engineering Conference in Garmisch, Germany, participants discussed what became known as the "software crisis": projects late, over budget and unreliable. The answer was engineering discipline, and with it a defined cycle.
- 1970: Waterfall. Winston W. Royce published "Managing the Development of Large Software Systems". Its sequential diagram later got the name Waterfall, although Royce himself warned that running it strictly one way was risky.
- 2001: Agile. The Agile Manifesto did not remove the phases. It made the cycle short and repeated it. A sprint is a small SDLC.
- 2009: DevOps. The term spread after the first DevOpsDays in Ghent. Deploy and Maintain became continuous: see CI/CD for WordPress.
- 2020s: AI. Coding tools made Build cheap. The other six phases did not get cheaper.
The weather changes. The cycle stays. That line closes our 40-second video on 4wp.dev/sdlc, where the umbrella stands through rain, lightning and falling stones.
SDLC From Three Sides: Client, Project, Developer
| Phase | Client asks | Project asks | Developer asks |
|---|---|---|---|
| Plan | Why are we doing this, and what is it worth? | Scope, budget, deadline, risks. | Is it feasible on WordPress? Existing plugin, custom plugin or theme code? |
| Requirements | What must the site do for my users? | Turn wishes into a list that can be accepted or rejected. | Roles and capabilities, content types, edge cases, integrations. |
| Design | How will it look and feel? | Is the solution the right size for the budget? | Data model, hooks, blocks or templates, REST routes, where each piece of code lives. |
| Build | When can I see it? | Progress against the plan. | Plugin and theme code, migrations, configuration. |
| Test | Does it work on my phone? | Is it ready to ship? | Unit and end-to-end tests, coding standards, capabilities, nonces, escaping. |
| Deploy | Is it live? | Release window and rollback plan. | Staging to production, WP-CLI, database, cache. |
| Maintain | Will it keep working? | Support cost and update schedule. | Core, plugin and PHP updates, security fixes, monitoring. |
On a small WordPress project one person often wears all three hats. A freelancer is the project manager and the developer, and often helps the client decide what they want. That is where SDLC stops being a manager's word.
SDLC in WordPress Development: Phase by Phase
Every rib already has a guide on 4wp.dev:
- Plan: Lean (MVP), Design Thinking.
- Requirements: BDD, Ubiquitous Language.
- Design: Architectures, SOLID, Domain-Driven Design, API-first, Block-first.
- Build: Hooks, Gutenberg Blocks, REST API, WordPress Coding Standards.
- Test: TDD, Security.
- Deploy: CI/CD for WordPress, WP-CLI, Twelve-Factor App.
- Maintain: Site Reliability Engineering, WP-CLI profiling.
From WordPress Developer to Tech Lead
Build is one rib out of seven. A developer who only builds competes with every tool that builds.
A developer who holds all seven asks why before writing code, pins down what "done" means, decides where the code lives, proves it works, ships it safely and keeps it alive. That developer is already doing a tech lead's job, whatever the title says.
The AI era asks for exactly this: not a developer who types fast, but a fullstack developer who thinks like an architect.
SDLC and AI: AI Took One Rib
AI coding tools write code fast. They do not decide what to build, they do not own the trade-offs, and they do not own the rollback.
- Vague requirements give you vague code, only faster.
- More generated code means more code to review and test.
- Architecture decides whether generated code fits the system or fights it.
AI took Build. Six ribs are still yours. More on how we split the work with agents at 4wp.dev: AI Workflows for WordPress and The Price of Attention.
SDLC FAQ
What does SDLC stand for?
Software Development Life Cycle: the phases software goes through from an idea to retirement.
What are the phases of SDLC?
Plan, Requirements, Design, Build, Test, Deploy and Maintain. Some sources merge or split them, but the order stays the same.
Is SDLC the same as Waterfall?
No. Waterfall is one way to walk through the cycle: one phase after another, once. Agile, Scrum and Kanban walk through the same phases in short, repeated loops.
Is SDLC still relevant with Agile and AI?
Yes. Agile made the cycle shorter, DevOps made Deploy and Maintain continuous, and AI made Build cheaper. None of them removed a phase.
Does a solo WordPress developer need SDLC?
Yes, more than anyone. A solo developer is the planner, the architect, the tester and the support team. Knowing the phases helps you see which one you skipped.
On 4wp.dev this FAQ is wrapped in our own plugin, 4WP FAQ: it adds FAQPage JSON-LD to the core Accordion.
Forecast for 2027: Sunny ☀️
Since we are talking about weather: want it on your site today? 4WP Weather is our Gutenberg block with full settings. Elementor widget? Coming in 2027. Promise.
More From 4wp.dev
- Methodologies: every way to walk under the umbrella.
- Architectures and SOLID: the Design rib.
- WP-CLI and REST API: the Build and Deploy ribs.
- 4WP Plugins: what we build with this cycle.
The SDLC Umbrella is a 4wp.dev model. Originally published on 4wp.dev/sdlc, where you can scroll through sixty years of weather and open every phase as the client, the project and the developer see it.
Anatoliy Dovgun, 4wp.dev. About WordPress, with love, from developers who love it.
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