<?php
/*
Plugin Name: Mod rewrite and disable Canonical URL Redirection
Description: Mod rewrite and Disables the "Canonical URL Redirect"
Version: 1.0
*/

function dcur_rewriteRulesArray($rules){

    $addRules = array();

    $addRules['catalog(\/.+)?'] = 'index.php?page_id=500';

    return $addRules + $rules;
}

add_filter('rewrite_rules_array', 'dcur_rewriteRulesArray');

function dcur_rewriteFlush(){
    flush_rewrite_rules();
}

function dcur_activate() {
    dcur_rewriteFlush();
}

function dcur_deactivate() {
    dcur_rewriteFlush();
}

register_activation_hook( __FILE__, 'dcur_activate' );
register_deactivation_hook( __FILE__, 'dcur_deactivate' );

add_action( 'init', 'dcur_rewriteFlush' );

function dcur_checkCanonical($redirect_url, $requested_url) {
    $params = parse_url($requested_url, PHP_URL_PATH);

    if (preg_match('#^\/catalog\/#i', $params)) {
        return true;
    }

    return $redirect_url;
}

add_filter('redirect_canonical', 'dcur_checkCanonical', 10, 2);