How to Cache Composer Dependencies in GitHub Actions

Cache the Composer cache directory keyed on composer.lock so packages are fetched once and reused.

Composer caches downloads in a directory reported by composer config cache-files-dir. Cache that path keyed on composer.lock, then run composer install to reuse it.

Steps

• Read the cache directory with composer config cache-files-dir.
• Cache that path keyed on composer.lock.
• Run composer install --prefer-dist to pull from the cache.

Workflow

steps:
  - id: composer-cache
    run: echo "dir=$(composer config cache-files-dir)" >> "$GITHUB_OUTPUT"
  - uses: actions/cache@v4
    with:
      path: ${{ steps.composer-cache.outputs.dir }}
      key: composer-${{ runner.os }}-${{ hashFiles('composer.lock') }}
      restore-keys: composer-${{ runner.os }}-
  - run: composer install --prefer-dist --no-progress

Gotchas

• Cache the download cache, not vendor/, so autoload maps regenerate correctly.
• Without composer.lock, key on composer.json instead but expect looser hits.

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