Redirect single post to external link - WordPress

gistfile1.txt

/**
     * =============================================================
     * Redirect single post to external link
     * =============================================================
     */
    // this checks to make sure that the function doesn't already exist
    // if something else in your WP uses a function named redirect_cpt_to_external_link
    // this check to see whether it exists or not will keep your site from crashing
    if ( ! function_exists('redirect_cpt_to_external_link') ) {
 
        // you add the action onto template_redirect
        add_action( 'template_redirect', 'redirect_cpt_to_external_link' );
   
        function redirect_cpt_to_external_link() {
   
            // this is ACF method of grabbing field data with get_field() function
            // the ACF field type is a "link"
            //
            // if you are using standard metaboxes you'd use the WP core function
            // get_post_meta https://developer.wordpress.org/reference/functions/get_post_meta/
            //
            $external_link = get_field('YOUR-ACF-FIELD-NAME');
   
            // here you check to make sure that you are ONLY redirecting for a custom post type with is_singular()
            // and you are checking to make sure that the external link field actually exists
            if ( is_singular( 'YOUR-CUSTOM-POST-TYPE' ) && ! empty( $external_link ) ) :
 
                    // then you 301 redirect with wp_redirect
                    wp_redirect( esc_url( $external_link ), 301 );
                    // always exit after wp_redirect()
                    exit;
            endif;
   
        }
 
    }

@badg0003 - Thank you so much. That's a great call. I've updated it. Thanks again for letting me know, greatly appreciated!