explain the step updating the git submodule reference in web/php.git
Merge branch 'PHP-5.3' into PHP-5.4

* PHP-5.3:
  explain the step updating the git submodule reference in web/php.git
Merge branch 'PHP-5.4' into PHP-5.5

* PHP-5.4:
  explain the step updating the git submodule reference in web/php.git
Merge branch 'PHP-5.5'

* PHP-5.5:
  explain the step updating the git submodule reference in web/php.git