Together PHP and JavaScript rule the web development market. Both are used on small, middle and even high-level sites, but before talking about the languages itself, we should clarify the way client and server work together. The following images show, what happens when you trigger a simple web address:

PHP
This C-like language is especially designed for server usage and simplicity while developing. It’s possible to use a lot more languages on the server-side, but PHP is pre-installed in nearly all web hosting offers.
PHP supports class-based object-oriented programming even though its core functionality is procedural. The PHP project is hosted at www.php.net, where they offer PHP and its nice documentation.
PHP is a powerful platform, but integrated functions do not follow unified rules for names and parameters. Additionally PHP offers a wide range of syntax elements and – sadly – some alternative syntaxes, making it more difficult for beginners to read sources from different developers.

<?php
$product = 'eyeos';
if ($product === 'oneye') {
	echo 'You are already using the latest community.';
} else {
	echo 'Please update your community.';
}
?>

Did you know?
“PHP” stands for “PHP: Hypertext Preprocessor” and as such it’s a recursive acronym (source).