Update minimum required PHP version to 5.3.23

- Per discussion on the ML, and per technical issues we've been attempting to
  resolve within the framework.
Merging PR #5602
Merge branch 'weierophinney-feature/new-minimum-php-version' into develop

* weierophinney-feature/new-minimum-php-version:
  Update minimum required PHP version to 5.3.23