Tired of hitting the Save Permalinks button every time you register a post type in WordPress? Try this function: it grabs the cached rewrite rules, checks for a target (could be anything, but let's say it's a post type with an archive) and flushes the rules if the rewrite rule isn't present.

maybe_flush.php

<?php 

function maybe_flush_rewrite_rules($target) {
    $rules = get_option( 'rewrite_rules' );
    
    if ( $rules[ $target . '/?$' ] !=  'index.php?post_type=' . $target ) {
        flush_rewrite_rules( $hard = true );
    }
}

// use it like this:
// first register your post type

function register_your_post_type(
  $args = array(
    //anything in here
    'has_archive' => true
  )
  register_post_type( 'your_post_type', $args )
);

// hook it to init
add_action( 'init', 'register_your_post_type' );

// then pass the post type name to maybe flush rewrite rules
maybe_flush_rewrite_rules( 'your_post_type' );

?>