improve documentation
Merge branch 'experimental/php' into refs/top-bases/experimental/marc

* experimental/php:
  improve documentation
Merge commit 'refs/top-bases/experimental/marc' into experimental/marc

* commit 'refs/top-bases/experimental/marc':
  improve documentation
Merge branch 'experimental/marc' into refs/top-bases/experimental/x-updates

* experimental/marc:
  improve documentation
Merge commit 'refs/top-bases/experimental/x-updates' into experimental/x-updates

* commit 'refs/top-bases/experimental/x-updates':
  improve documentation