Ticket #14349: wp-query-manipulation.php

<?php

class WP_Query_Manipulation {

        private $bits = array();
        private $wp_query;

        function __construct( $callback ) {

                $this->callback = $callback;

                $filters = array(
                        'posts_where',
                        'posts_join',
                        'posts_groupby',
                        'posts_orderby',
                        'posts_distinct',
                        'post_limits',
                        'posts_fields'
                );

                foreach ( $filters as $filter ) {
                        add_filter( $filter, array( $this, 'collect' ), 999, 2 );
                        add_filter( $filter . '_request' , array( $this, 'update' ), 9 );
                }

                add_action( 'posts_selection' , array( $this, 'alter' ) );
        }

        function collect( $value, $wp_query ) {
                // remove 'posts_'
                $key = explode( '_', current_filter() );
                $key = array_slice( $key, 1 );
                $key = implode( '_', $key );

                $this->bits[ $key ] = $value;

                $this->wp_query = $wp_query;

                return $value;
        }

        function alter($query) {
                $this->bits = call_user_func( $this->callback, $this->bits, $this->wp_query );
        }

        function update( $value ) {
                // remove 'posts_' and '_request'
                $key = explode( '_', current_filter() );
                $key = array_slice( $key, 1, -1 );
                $key = implode( '_', $key );

                return $this->bits[ $key ];
        }
}


// TESTING
function test_wp_query_manipulation( $bits, $wp_query ) {
        foreach ( $bits as $key => &$value )
                $value = "[$key]";

        return $bits;
}
new WP_Query_Manipulation( 'test_wp_query_manipulation' );

function debug_wp_query_manipulation() {
        var_dump( $GLOBALS['wp_query']->request );
}
add_filter( 'the_posts', 'debug_wp_query_manipulation' );