Facebook Pixel helps organizations measure customer actions, build audiences and unlock optimisation tools. Facebook pixel is a snippet of JavaScript code that allows you to track visitor activity on your website.
PHP: Hypertext Preprocessor is a server-side scripting language designed for Web development, but also used as a general-purpose programming language. PHP code may be embedded into HTML code, or it can be used in combination with various web template systems, web content management systems, and web frameworks.