Get the content of a webpage into a PHP variable

This is a very basic thing to do with cURL, but with endless possibilities. Once you have a webpage in a PHP variable, you can for example, retrieve a particular information on the page to use on your own website.

<?php
    ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, "example.com");
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    $output = curl_exec($ch);
    curl_close($ch);
?>