ready.php

<?php namespace ProcessWire;

/**
 * ProcessWire Bootstrap API Ready 
 * ===============================
 * This ready.php file is called during ProcessWire bootstrap initialization process.
 * This occurs after the current page has been determined and the API is fully ready 
 * to use, but before the current page has started rendering. This file receives a 
 * copy of all ProcessWire API variables. This file is an idea place for adding your
 * own hook methods. 
 *
 */

if(!defined("PROCESSWIRE")) die();

/** @var ProcessWire $wire */

/**
 * Example of a custom hook method
 * 
 * This hook adds a “numPosts” method to pages using template “category”.
 * The return value is the quantity of posts in category.
 *
 * Usage:
 * ~~~~~
 * $numPosts = $page->numPosts(); // returns integer
 * numPosts = $page->numPosts(true); // returns string like "5 posts"
 * ~~~~~
 *
 */
$wire->addHook('Page(template=category)::numPosts', function($event) {
	/** @var Page $page */
	$page = $event->object;

	// only category pages have numPosts
	if($page->template->name !== 'category') return;

	// find number of posts
	$numPosts = $event->pages->count("template=blog-post, categories=$page");

	if($event->arguments(0) === true) {
		// if true argument was specified, format it as a "5 posts" type string
		$numPosts = sprintf(_n('%d post', '%d posts', $numPosts), $numPosts);
	}

	$event->return = $numPosts;
});