With the same set of pool configuration files, we can have two states:
- when it operates correctly (e.g. our PHP 5.6.2), it loads all configuration files and listens to every port.
- when it doesn't operate correctly (e.g. the PHP 5.5.x through FreeBSD ports), it only launch some pools, but not all
Reinstalling a genuine PHP compilation instead of a package/port worked for PHP 5.5.x to fix the issue, but not for PHP 5.6.x.