CI/CD Pipeline Knowledge Base

Quick reference for CI/CD pipeline patterns, platforms, and best practices.

Pipeline Stages

┌─────────────┐    ┌─────────────┐    ┌─────────────┐    ┌─────────────┐    ┌─────────────┐
│   Install   │───▶│    Lint     │───▶│    Test     │───▶│    Build    │───▶│   Deploy    │
└─────────────┘    └─────────────┘    └─────────────┘    └─────────────┘    └─────────────┘
     Deps            Code Style         PHPUnit           Docker            Production
     Cache           PHPStan            Coverage          Artifacts         Environments

Standard PHP Pipeline:

1. Install — Composer dependencies, cache restore
2. Lint — PHPStan, Psalm, PHP-CS-Fixer, DEPTRAC
3. Test — PHPUnit, code coverage, mutation testing
4. Build — Docker image, version tagging
5. Deploy — Environment deployment, health checks

Platform Comparison

Feature	GitHub Actions	GitLab CI
Config file	.github/workflows/*.yml	.gitlab-ci.yml
Runners	GitHub-hosted / self-hosted	GitLab-hosted / self-hosted
Caching	actions/cache	Built-in cache:
Artifacts	actions/upload-artifact	Built-in artifacts:
Secrets	Repository/Environment secrets	CI/CD Variables
Matrix builds	strategy.matrix	parallel:matrix
Reusable	Composite actions, workflows	include:, extends:
Container	container:	image:

GitHub Actions Structure

name: CI Pipeline

on:
  push:
    branches: [main, develop]
  pull_request:
    branches: [main]

env:
  PHP_VERSION: '8.4'
  COMPOSER_CACHE_DIR: ~/.composer/cache

jobs:
  lint:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: shivammathur/setup-php@v2
        with:
          php-version: ${{ env.PHP_VERSION }}
          coverage: none
      - name: Cache Composer
        uses: actions/cache@v4
        with:
          path: ${{ env.COMPOSER_CACHE_DIR }}
          key: composer-${{ hashFiles('composer.lock') }}
      - run: composer install --no-progress --prefer-dist
      - run: vendor/bin/phpstan analyse

  test:
    needs: lint
    runs-on: ubuntu-latest
    services:
      mysql:
        image: mysql:8.0
        env:
          MYSQL_DATABASE: test
          MYSQL_ROOT_PASSWORD: root
        ports:
          - 3306:3306
    steps:
      - uses: actions/checkout@v4
      - uses: shivammathur/setup-php@v2
        with:
          php-version: ${{ env.PHP_VERSION }}
          coverage: xdebug
      - run: composer install --no-progress --prefer-dist
      - run: vendor/bin/phpunit --coverage-clover coverage.xml
      - uses: codecov/codecov-action@v4

GitLab CI Structure

stages:
  - install
  - lint
  - test
  - build
  - deploy

variables:
  PHP_VERSION: "8.4"
  COMPOSER_CACHE_DIR: "$CI_PROJECT_DIR/.composer-cache"

.php_template: &php_template
  image: php:${PHP_VERSION}-cli
  cache:
    key: composer-$CI_COMMIT_REF_SLUG
    paths:
      - .composer-cache/
      - vendor/
    policy: pull

install:
  <<: *php_template
  stage: install
  cache:
    policy: pull-push
  script:
    - composer install --no-progress --prefer-dist

lint:phpstan:
  <<: *php_template
  stage: lint
  needs: [install]
  script:
    - vendor/bin/phpstan analyse --memory-limit=1G

test:unit:
  <<: *php_template
  stage: test
  needs: [lint:phpstan]
  services:
    - mysql:8.0
  variables:
    MYSQL_DATABASE: test
    MYSQL_ROOT_PASSWORD: root
  script:
    - vendor/bin/phpunit --coverage-cobertura coverage.xml
  coverage: '/^\s*Lines:\s*\d+.\d+\%/'
  artifacts:
    reports:
      coverage_report:
        coverage_format: cobertura
        path: coverage.xml

Caching Strategies

Composer Cache

GitHub Actions:

- name: Cache Composer dependencies
  uses: actions/cache@v4
  with:
    path: |
      ~/.composer/cache
      vendor
    key: php-${{ hashFiles('composer.lock') }}
    restore-keys: |
      php-

GitLab CI:

cache:
  key:
    files:
      - composer.lock
  paths:
    - .composer-cache/
    - vendor/
  policy: pull-push  # pull on jobs, push on install

Docker Layer Cache

GitHub Actions:

- name: Set up Docker Buildx
  uses: docker/setup-buildx-action@v3

- name: Build and push
  uses: docker/build-push-action@v5
  with:
    context: .
    cache-from: type=gha
    cache-to: type=gha,mode=max

GitLab CI:

build:
  script:
    - docker build --cache-from $CI_REGISTRY_IMAGE:latest -t $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA .

Parallelization Patterns

Matrix Strategy (GitHub Actions)

test:
  strategy:
    matrix:
      php: ['8.2', '8.3', '8.4']
      database: ['mysql', 'postgres']
      exclude:
        - php: '8.2'
          database: 'postgres'
    fail-fast: false
  runs-on: ubuntu-latest
  steps:
    - run: echo "Testing PHP ${{ matrix.php }} with ${{ matrix.database }}"

Parallel Jobs (GitLab CI)

test:
  parallel:
    matrix:
      - PHP_VERSION: ['8.2', '8.3', '8.4']
        DATABASE: ['mysql', 'postgres']
  script:
    - echo "Testing PHP $PHP_VERSION with $DATABASE"

Test Splitting

# Split PHPUnit tests across runners
test:
  parallel: 4
  script:
    - vendor/bin/phpunit --testsuite unit --filter "Test$((($CI_NODE_INDEX - 1) * 25 + 1))-$(($CI_NODE_INDEX * 25))"

Environment Management

GitHub Environments

deploy-production:
  runs-on: ubuntu-latest
  environment:
    name: production
    url: https://example.com
  steps:
    - name: Deploy
      env:
        DATABASE_URL: ${{ secrets.DATABASE_URL }}
      run: ./deploy.sh

GitLab Environments

deploy:production:
  stage: deploy
  environment:
    name: production
    url: https://example.com
  rules:
    - if: $CI_COMMIT_BRANCH == "main"
  script:
    - ./deploy.sh

Artifact Management

Test Reports

GitHub Actions:

- name: Upload test results
  uses: actions/upload-artifact@v4
  if: always()
  with:
    name: test-results
    path: |
      coverage.xml
      junit.xml
    retention-days: 30

GitLab CI:

test:
  artifacts:
    when: always
    paths:
      - coverage.xml
    reports:
      junit: junit.xml
      coverage_report:
        coverage_format: cobertura
        path: coverage.xml
    expire_in: 30 days

Pipeline Optimization Checklist

Optimization	Impact	Implementation
Dependency caching	⬇️ 2-5 min	Cache composer, npm
Docker layer caching	⬇️ 3-10 min	BuildKit cache
Parallel jobs	⬇️ 50-80%	Matrix, split tests
Skip unchanged	⬇️ Variable	Path filters, needs
Smaller images	⬇️ 1-3 min	Alpine, multi-stage
Fail fast	⬇️ Variable	Early exit on errors

Common Pipeline Patterns

1. Monorepo Pipeline

# Only run when specific paths change
on:
  push:
    paths:
      - 'services/api/**'
      - 'shared/**'

2. Pull Request vs Push

on:
  pull_request:
    # Run tests, skip deploy
  push:
    branches: [main]
    # Run full pipeline with deploy

3. Scheduled Security Scans

on:
  schedule:
    - cron: '0 0 * * 1'  # Weekly Monday
  workflow_dispatch:  # Manual trigger

4. Release Workflow

on:
  release:
    types: [published]

jobs:
  publish:
    steps:
      - name: Get version
        run: echo "VERSION=${GITHUB_REF#refs/tags/v}" >> $GITHUB_ENV

Best Practices

DO

• ✅ Cache dependencies aggressively
• ✅ Use specific action versions (@v4, not @latest)
• ✅ Fail fast in PR pipelines
• ✅ Run security scans on schedule
• ✅ Use environments for deployment gates
• ✅ Store secrets in vault, not code

DON'T

• ❌ Run full pipeline on every commit
• ❌ Install dependencies in every job
• ❌ Use mutable tags for Docker images
• ❌ Expose secrets in logs
• ❌ Skip tests for "quick fixes"
• ❌ Deploy without health checks

References

For detailed information, load these reference files:

• references/github-actions.md — GitHub Actions deep dive
• references/gitlab-ci.md — GitLab CI configuration
• references/caching.md — Caching strategies and patterns