PHP is a popular scripting language that is designed to produce dynamic web pages (e.g. login pages, shopping carts).
PHP code is embedded into the html source of a website, and is run on the web hosting server rather than on the browser. So, if you look at the source code of a PHP web page, the code that you see is just plain HTML. Since PHP is a universal scripting language, websites created with PHP are fully compatible with popular mobile devices like iPhone and iPad. A large number popular websites, including Facebook and Wikipedia, are written in PHP.
WordPress, Drupal, and Joomla are the most commonly-used open source content management systems written in PHP. A lot of webmasters choose these three platforms to build their websites because of their flexibility. There are a lot of themes and plugins created for these three platforms and webmasters can create professional looking websites based on these systems with just a few clicks. Also, their themes are customizable, so webmasters can change the coding to fit their needs.
PHP AND WEB HOSTING
As mentioned before, PHP is decoded on the web hosting server side. Therefore, if the website is written in PHP, it needs to be hosted on a server that has PHP processor module. It is important to check with your web hosting provider if the hosting plan you are using supports PHP.