wordpress custom url rewrites

gistfile1.php

<?php
/***********************************************************************************************************/
/********************* WRITE OUR CUSTOM REWRITE RULES IN WORDPRESS *****************************************/
/***********************************************************************************************************/
add_action( 'init', 'add_custom_rewrite_rules' );  
function add_custom_rewrite_rules() {   
  global $wp_rewrite;  
  $new_rules = array(  
    "blog/city/([^/]+)/([^/]+)/?" => "index.php?city_tags=\$matches[2]"
  );  
  $wp_rewrite->extra_rules_top += $new_rules;  

/*echo "<pre>";
print_r($wp_rewrite);
echo "</pre>";
exit;*/

}  
/***********************************************************************************************************/
/***********************************************************************************************************/