xkcd.php

<?php
class XkcdParser
{
	/* @var array $last Data of the latest comic */
	private $last;

	/* @var int $max Latest comic data ID */
	private $max;

	public function __construct()
	{
		$this->last = $this->query();
		$this->max = $this->last['num'];
	}

	/*
	 * returns a random xkcd comic, from 1 to last
	 * @see $this->last, $this->max
	 * @api
	 *
	 * @return array the comic data
	 */
	public function random()
	{
		$id = rand(1, $this->max);
		return $this->query($id);
	}

	/*
	 * queries data for the specified comic
	 * @api
	 *
	 * @param int|string id Comic id or empty string for latest
	 */
	public function query($id = '')
	{
		if ($id == '' && $this->last)
			return $last;
		$url = $this->url($id);
		return json_decode(file_get_contents($url), true);
	}

	/*
	 * displays a comic
	 * @param array $data the comic data ({@see query})
	 * @return void
	 */
	public function display($data)
	{
		echo "
<img src='${data['img']}' />
<p>${data['alt']}</p>
";
	}

	/*
	 * Returns the JSON url for the specified comic
	 *
	 * @param int|strign $id Comic id or empty string for latest
	 * @return string Full URL
	 */
	private function url($id = '')
	{
		return 'http://xkcd.com/' . ($id ? "$id/" : '') . 'info.0.json';
	}
}

$xkcd = new XkcdParser();
$xkcd->display($xkcd->random());