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Legacy to Symfony

The Enterprise Blueprint for Zero-Downtime PHP Migrations

This book is 95% completeLast updated on 2026-05-25
Kerrial Beckett Newham

The difference between a migration that ships and one that gets quietly abandoned is not the quality of the code. It is the quality of the process.

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About

About

About the Book

For a mid-sized to enterprise PHP application, a comprehensive full-stack migration ranges from approximately 100,000 to 200,000 EUR on average depending on size and complexity. It will run for months, cross financial quarters, and put the engineer leading it under a level of organisational pressure that no amount of clean architecture prepares them for. The difference between a migration that ships and one that gets quietly abandoned is not the quality of the code. It is the quality of the process.

This is the book that documents this process end to end.

  

Legacy to Symfony is a complete, opinionated blueprint for migrating a PHP monolith to Symfony with zero server downtime. It covers every layer of the application — infrastructure, database, authentication, business logic, templates, and deployment — with exact tooling, real CLI output, and architectural decisions drawn from real world migrations. It also covers what technical books consistently ignore: the organisational side of a project this long — managing the politics and pressure, communicating with stakeholders and keeping a team focused when the business loses patience. Not theory. Just a process that works.

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Author

About the Author

Kerrial Beckett Newham

A passionate developer driven by a desire to create and build. Kerrial embarked on a journey into web development fuelled by a deep enjoyment of the process. This journey led to self-taught mastery of PHP, collaborating on projects with major industry players, and humble startup initiatives. With a diverse background spanning nearly a decade, ranging from telecommunications to social media platforms, Kerrial brings a wealth of practical experience to the orchestra, with a writing style characterised by practicality, directness, and simplicity.

Contents

Table of Contents

Introduction: The Migration Manifesto

  1. The Myth of the Invisible Migration
  2. The “Velocity Debt” Equation
  3. The “Dead Horse” Protocol
  4. The Other Half of the Problem

Chapter 1: Triage & Containment

  1. The “Bin It or Build It” Audit
  2. Calculating the Rot
  3. The Three Red Flags of a Rewrite
  4. The Risk Language Problem
  5. The “Go/No-Go” Meeting

Chapter 2: Mapping the Monolith

  1. The Horizontal Trap
  2. Identifying Bounded Contexts
  3. The Dependency Graph
  4. Choosing the First Target

Chapter 3: The Morale Boost (Dockerizing Legacy)

  1. Containing the Rot

Chapter 4: Strategy & Routing

  1. The Strangler Fig Proxy
  2. Enter Traefik: The Dynamic Router
  3. The Psychology of the Rollback
  4. The Rollback Strategy

Chapter 5: Taming the Legacy Database

  1. The Single Source of Truth
  2. The Doctrine Collision
  3. Enter Indoctrinate
  4. The Shared Database Concurrency Trap

Chapter 6: Authentication Continuity

  1. Evaluating Your Options
  2. The Shared Session Bridge in Practice
  3. Mapping Legacy Roles with LegacyRoleVoter
  4. The Failure Modes
  5. Wiring It Together

Chapter 7: First Blood

  1. Bootstrapping Symfony
  2. Governing the New Codebase from Day One
  3. Connecting Doctrine to the Shared Database
  4. Generating Doctrine Entities
  5. Multiple Databases
  6. Automating the Code Transformation with Rector
  7. The Manual Review Pass
  8. Wiring Up Traefik
  9. The First Deployment

Chapter 8: Migrating the View Layer

  1. The view-converter Tool
  2. What the Tool Converts
  3. What the Tool Flags
  4. The Template Manual Review Pass
  5. The Data Contract Has Changed
  6. Wiring the Template into Symfony
  7. Verifying the Converted Template
  8. The JavaScript in the View Layer
  9. Converting jQuery to Vanilla JS
  10. Converting Vanilla JS to a Stimulus Controller
  11. Connecting the Controller to the Markup

Chapter 9: The Psychology of Project Ownership

  1. The Identity Trap
  2. The Day I Stopped Being the Consultant
  3. The Messenger Framework
  4. The Sunk-Cost Trap
  5. Communicating Bad News Without Becoming the Bad News
  6. Detaching From Code You Originally Wrote
  7. What Success Actually Looks Like

Chapter 10: The Role of AI in a Migration

  1. The Wrong Way to Use AI in a Migration
  2. Understanding Code You Have Never Seen Before
  3. Writing Custom Rector Rules with AI
  4. Closing the Manual Review Pass Gaps
  5. Generating Characterisation Tests from Legacy Behaviour
  6. The Limits of AI in a Migration

Chapter 11: The Sprint Cadence

  1. The Loop
  2. Tracking the Burn-Down
  3. Communicating Progress
  4. When a Sprint Stalls
  5. The Cadence Is the Project

Chapter 12: Killing the Legacy Container

  1. The Final Sprint Is Not Special
  2. Flipping the Proxy
  3. Verifying Zero Legacy Traffic
  4. Removing the Legacy Container
  5. Renaming the Database Container
  6. Cleaning Up Migration Artefacts
  7. What the Dependency Graph Looks Like Now

Chapter 13: Post-Migration Hardening

  1. Maturing the CI Pipeline
  2. Deployment
  3. Monitoring
  4. The Performance Baseline
  5. The Migration Is Complete

Chapter 14: Reclaiming the Schema

  1. The Expand/Contract Pattern
  2. Running indoctrinate on the Live Schema
  3. Prioritising the Work
  4. Cleaning Up Doctrine Entity Mappings
  5. The Schema Is Yours

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