PHP HyperText Preprocessor is a scripting language that runs on a server. This language is the most common way data is moved between a web application (front end) and the server (back-end). Common examples include:
<?php
if ($_POST['sendRequest']) {
$sendTo = $_POST['destinationEmail'];
$subject = "Web inquiry";
$message = $_POST['emailInquiry'];
mail($sendTo, $subject, $message);
}
?>
PHP drives most content management systems (like Drupal and WordPress). When you search for a book on Amazon.com, you don't land on an HTML page someone has created for that book; PHP pulls data from Amazon's database and arranges it in an HTML template.