class-rewrite.php

<?php
/**
 * @package Frontend
 */

if ( !defined('WPSEO_VERSION') ) {
	header('HTTP/1.0 403 Forbidden');
	die;
}

/**
 * This code handles the category rewrites.
 */
class WPSEO_Rewrite {

	/**
	 * Class constructor
	 */
	function __construct() {
		add_filter( 'query_vars', array( $this, 'query_vars' ) );
		add_filter( 'category_link', array( $this, 'no_category_base' ) );
		add_filter( 'request', array( $this, 'request' ) );
		add_filter( 'category_rewrite_rules', array( $this, 'category_rewrite_rules' ) );

		add_action( 'created_category', array( $this, 'schedule_flush' ) );
		add_action( 'edited_category', array( $this, 'schedule_flush' ) );
		add_action( 'delete_category', array( $this, 'schedule_flush' ) );

		add_action( 'init', array( $this, 'flush' ), 999 );
	}

	/**
	 * Save an option that triggers a flush on the next init.
	 *
	 * @since 1.2.8
	 */
	function schedule_flush() {
		update_option( 'wpseo_flush_rewrite', 1 );
	}

	/**
	 * If the flush option is set, flush the rewrite rules.
	 *
	 * @since 1.2.8
	 */
	function flush() {
		if ( get_option( 'wpseo_flush_rewrite' ) ) {
			add_action( 'shutdown', 'flush_rewrite_rules' );
			delete_option( 'wpseo_flush_rewrite' );
		}
	}

	/**
	 * Override the category link to remove the category base.
	 *
	 * @param string $link     Unused, overridden by the function.
	 * @return string
	 */
	function no_category_base( $link ) {
		$category_base = get_option( 'category_base' );

		if ( '' == $category_base )
			$category_base = 'category';

		// Remove initial slash, if there is one (we remove the trailing slash in the regex replacement and don't want to end up short a slash)
		if ( '/' == substr( $category_base, 0, 1 ) )
			$category_base = substr( $category_base, 1 );

		$category_base .= '/';

		return preg_replace( '`' . preg_quote( $category_base, '`' ) . '`u', '', $link, 1 );
	}

	/**
	 * Update the query vars with the redirect var when stripcategorybase is active
	 *
	 * @param $query_vars
	 * @return array
	 */
	function query_vars( $query_vars ) {
		$options = get_wpseo_options();

		if ( isset( $options['stripcategorybase'] ) && $options['stripcategorybase'] )
			$query_vars[] = 'wpseo_category_redirect';

		return $query_vars;
	}

	/**
	 * Redirect the "old" category URL to the new one.
	 *
	 * @param array $query_vars Query vars to check for existence of redirect var
	 * @return array
	 */
	function request( $query_vars ) {
		if ( isset( $query_vars['wpseo_category_redirect'] ) ) {
			$catlink = trailingslashit( get_option( 'home' ) ) . user_trailingslashit( $query_vars['wpseo_category_redirect'], 'category' );

			wp_redirect( $catlink, 301 );
			exit;
		}
		return $query_vars;
	}

	/**
	 * This function taken and only slightly adapted from WP No Category Base plugin by Saurabh Gupta
	 *
	 * @return array
	 */
	function category_rewrite_rules() {
		global $wp_rewrite;

		$category_rewrite = array();

		$taxonomy = get_taxonomy('category');

		$blog_prefix = '';
		if ( function_exists( 'is_multisite' ) && is_multisite() && !is_subdomain_install() && is_main_site() )
			$blog_prefix = 'blog/';

		foreach ( get_categories( array( 'hide_empty'=> false ) ) as $category ) {
			$category_nicename = $category->slug;
			if ( $category->parent == $category->cat_ID ) // recursive recursion
				$category->parent = 0;
			elseif ( $taxonomy->rewrite['hierarchical'] != 0 && $category->parent != 0 )
				$category_nicename = get_category_parents( $category->parent, false, '/', true ) . $category_nicename;

			$category_rewrite[$blog_prefix . '(' . $category_nicename . ')/(?:feed/)?(feed|rdf|rss|rss2|atom)/?$'] = 'index.php?category_name=$matches[1]&feed=$matches[2]';
			$category_rewrite[$blog_prefix . '(' . $category_nicename . ')/page/?([0-9]{1,})/?$']                  = 'index.php?category_name=$matches[1]&paged=$matches[2]';
			$category_rewrite[$blog_prefix . '(' . $category_nicename . ')/?$']                                    = 'index.php?category_name=$matches[1]';
		}

		// Redirect support from Old Category Base
		$old_base                          = $wp_rewrite->get_category_permastruct();
		$old_base                          = str_replace( '%category%', '(.+)', $old_base );
		$old_base                          = trim( $old_base, '/' );
		$category_rewrite[$old_base . '$'] = 'index.php?wpseo_category_redirect=$matches[1]';

		return $category_rewrite;
	}
}

global $wpseo_rewrite;
$wpseo_rewrite = new WPSEO_Rewrite();