• Silex PHP micro-framework
• tred – A non-opinionated PHP framework with a mind of it’s own, focused on security & scalability, while staying out of your way.

Databases

• Propel — an open-source Object-Relational Mapping (ORM) for PHP5.

Security

• Top 10 PHP best security practices

Templates

• Twig
  • Twig: creating and using templates

ZendFramework

• Getting Started with Zend Framework 1.11