create clean attachment URLs

image-url-fix

// clean URLs for attachments
// http://domain.com/?attachment_id=173
// http://domain.com/attachment/173

function rkv_attachment_urls($wp_rewrite){
  $new_rules = array();
  $new_rules['media/(\d*)$'] = 'index.php?attachment_id=$matches[1]';
  $wp_rewrite->rules = $new_rules + $wp_rewrite->rules;
}

function rkv_flush_rules() {
    $rules = get_option( 'rewrite_rules' );

    if ( ! isset( $rules['media/(\d*)$'] ) ) {
        global $wp_rewrite;
        $wp_rewrite->flush_rules();
    }
}

add_action('generate_rewrite_rules', 'rkv_attachment_urls');
add_action('wp_loaded', 'rkv_flush_rules');