Zend Framework is an open source, object-oriented web application framework implemented in PHP 5 and licensed under the New BSD License. Zend Framework”often referred to as ZF”is developed with the goal of simplifying web development while promoting best practices in the PHP developer community. ZF's use-at-will architecture allows developers to reuse components when and where they make sense in their applications without requiring other ZF components beyond minimal dependencies. There is therefore no single development paradigm or pattern that all Zend Framework users must follow, although ZF does provide components for the MVC and Table Gateway design patterns which are used in most ZF applications. Zend Framework provides individual components for many other common requirements in web application development, including authentication and authorization via access control lists (ACL), application configuration, data caching, filtering/validation of user-provided data for security and data integrity, internationalization, interfaces to AJAX functionality, email composition/delivery, Lucene-format search indexing and querying, and all Google Data APIs along with many other popular web services. Because of their loosely coupled design, ZF components can be used relatively easy alongside components from other PHP web application frameworks.