There are so many possibilities that this language has that so many people know how to use PHP and code in it and every day that number gets bigger.
PHP is easy to understand and the biggest advantage is that it has so many functions and options and its easy to install it in any hosting.
Every major hosting supports PHP which means that they have installed PHP software.
Optionally they have ASP and Perl installed but in most cases they have PHP support.
Its hard to find a hosting service that doesn't support PHP because for most of the websites you will surely encounter some PHP scripts that you will need to use or even PHP snippets which are needed in many cases.
Everyone recommend PHP scripts and Content management systems made in this language since it is easy to use and world wide recognized.
You can always get the latest PHP software from the official PHP homepage where you can find tutorials and tips of how to create or modify your PHP codes and snippets.
When you install PHP software on your server you can simply add support for that web language to users so they can install content management systems that are often connected with mysql databases and other regular software.
Php is also very used in presenting hosting templates so as you may find there is a big chance that you have some hosting template for your site made in PHP.
We can not say that PHP web language is the best language because you can find even in the last version some bugs but is surely the most used web language.
If you are in dilemma whether to use this and install this software or not you should first lookup all functions that this language has and on that base you can conclude how much you need this language.
But after all this is the closest you can get to the best web language.