In the beginning I would use doctrine ORM because the primary one however it was an overkill, needless features and most likely excessive calls. Among the primary reasons was the "assistant" that handled traverse trees (the hierarchy tree) easily but I am beginning to prefer building my very own class.

This is exactly what I am searching for:

1) Can manage multiple database connections, (kind of like doctrine manager)
2) Models
3) flexible

All suggestions are welcome

You should check out the PHP body fat-free framework http://fatfree.sourceforge.net/, it offers a 'mini-orm'

phpDataMapper are designed for master/slave plugs in addition to multiple different connections of various types. You simply pass your adapter towards the Mapper upon instantiation:

$postMapper = new PostMapper($adapter);
$postMapper = new PostMapper($masterAdapter, $slaveAdapter);

http://phpdatamapper.com/documentation/getting-started/

If you're searching for an ORM that implements the information Mapper paradigm but is not as heavy as Doctrine i quickly would highly recommend that you simply have a look at GacelaPHP.

Gacela Features:

  • Data mapper
  • Foreign key mapping
  • Association mapping
  • Dependent mapping
  • Concrete table inheritance
  • Query object
  • Metadata mapping
  • Lazy &lifier eager loading
  • Full Memcache support

Other ORM solutions are extremely bloated or have troublesome restrictions when developing anything remotely complicated. Gacela resolves the restrictions from the active record approach by applying the information Mapper Pattern and keep bloat low by utilizing PDO for those interactions using the DB and memcache.