PHP is a widely used scripting language that is mainly used for web development. It's a general-purpose scripting language and server-side programming of most websites you find in the internet are done using PHP.
It's not difficult to learn the language. However you should find out the best resources to learn PHP first. This is true for learning any new language. Here are three of the most renowned and popular websites you can use to learn PHP.
1. W3Schools PHP tutorial
W3Schools is the most popular resource in the web for learning web development. It's PHP tutorial has proved to be a great starting place for PHP learners.
This site includes a large number of tutorials to learn PHP aimed at beginners as well as many tips and tricks you can use with PHP.
3. PHP 101
This site has a step by step guide to learn PHP starting from the scratch. The tutorials are both informal and entertaining.