Framework
A framework is a library of code and practices that helps building PHP applications. Frameworks provide common features, such as forms, authentications, templating, database access and security.
Frameworks are often described as a platform: they stand as a layer above PHP, with its own conventions and behaviors. PHP is the language of the framework, and the language used to extend the framework.
Frameworks provide a set of tools and components to build applications, though they usually do not provide a comprehensive service out of the box: the framework must be used to build the application, usually in an original and creative way. For example, a framework may be used to build a forum or a CMS, while the opposite is rarely possible.
There are lots of frameworks written with PHP. In alphabetical order, here is a non exhaustive list:
Aura <https://auraphp.com/>_Bolt CMS <https://boltcms.io/>_Code Igniter <https://codeigniter.com/>_CakePHP <https://cakephp.org/>_Cappuccino <https://www.cappuccino.dev/>_Drupal <https://www.drupal.org/>_e107 <https://e107.org/>_FuelPHP <https://fuelphp.com/>_Gyroscope <https://www.gyro-php.org/>_Hyperf <https://github.com/hyperf/hyperf>_Ibexa <https://www.ibexa.co/>_Joomla <https://www.joomla.org/>_Koala <http://www.koala-framework.org/>_Laminas <https://getlaminas.org/>_Laravel <https://laravel.com/>_Leafphp <https://leafphp.dev/>_Light-php <https://github.com/bakeiro/Light-PHP.git>_LightMVC <https://github.com/lightmvc/lightmvcskel.git>_Lithium <https://li3.me/>_Medoo <https://medoo.in/>_Nette <https://nette.org/en/>_October <https://octobercms.com/>_Phalcon <https://phalcon.io/en-us>_Prado <http://www.pradoframework.net/site/>_Qcodo <https://github.com/qcodo/qcodo.git>_redcatphp <https://github.com/redcatphp/redcatphp>_Slim <https://www.slimframework.com/>_Symfony <https://symfony.com/>_Typo3 <https://typo3.org/>_Ubiquity <https://github.com/phpMv/ubiquity>_Wordpress <https://www.wordpress.org/>_X <https://github.com/clue/framework-x.git>_Yii <https://www.yiiframework.com/>_Zend Framework <https://framework.zend.com/>_
This is not an exhaustive list.