Technology & SaaS
PHP 5.6 to 8.3 Migration with Zero Downtime and 93% Faster Deployments
Migrating a project management SaaS from a monolithic PHP 5.6 codebase to a modern PHP 8.3 architecture, keeping the platform live throughout a ten-week migration.
What We Were Solving
The SaaS platform served 1,200 active teams but was built on PHP 5.6 with no separation of concerns. The monolithic codebase made changes risky as any modification could break unrelated features. Deployment took 45 minutes and required a maintenance window. The database schema had evolved organically over six years with no migration strategy, resulting in 340 unused columns and 89 redundant indexes. Three critical security patches could not be applied because the codebase was incompatible with newer PHP versions. Customer-reported bugs averaged 12 per month.
Our Strategic Approach
We migrated the platform to PHP 8.3 using an incremental strangler pattern that kept the live system running throughout. Each module was extracted, rewritten with strict typing and proper tests, and deployed behind a feature flag. Database schema was cleaned through a series of zero-downtime migrations that removed unused columns, optimised indexes, and normalised denormalised data. Deployment was automated with a CI pipeline reducing deploy time from 45 minutes to under 3. The new architecture supports proper staging environments enabling thorough testing before production releases.
Deliverables
- Full PHP 5.6 to 8.3 migration using strangler pattern
- Modular architecture with strict typing and separation of concerns
- Database schema cleanup removing 340 unused columns
- Automated CI/CD pipeline with sub-3-minute deployments
- Staging environment matching production configuration
- Comprehensive test suite covering critical user flows
- Security patches applied for all outstanding vulnerabilities
- Technical documentation and architecture decision records
Project Timeline
Codebase Audit
Mapped all modules, dependencies, database schema issues and security vulnerabilities. Designed migration sequence by risk and dependency.
Core Module Migration
Authentication, user management, project core and billing modules. Each extracted, rewritten and deployed behind feature flags.
Database and CI/CD
Schema cleanup migrations, index optimisation, CI/CD pipeline setup and staging environment.
Remaining Modules and Cutover
Secondary modules, test suite completion, feature flag removal and final cutover from legacy code paths.
Measurable Results
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