Metabox mit select zur Auswahl von Standard-Footer-CTA oder Alternative

<?php
// Add a Metabox to the backend
function add_nxt_custom_footer_cta() {
	add_meta_box("nxt-custom-footer-cta", "CTA im Footer-Bereich", "nxt_custom_footer_cta_construction", "page", "side", "high", null);
}
add_action("add_meta_boxes", "add_nxt_custom_footer_cta");

// Fill Metabox with our custom variable
function nxt_custom_footer_cta_construction() {
	wp_nonce_field(basename(__FILE__), "nxt-custom-footer-metabox-nonce");
	if(get_post_meta(get_the_ID(), '_nxt_footer_cta', true) != '') {
		$nxt_current_footer_cta = get_post_meta(get_the_ID(),'_nxt_footer_cta',true);
		echo '<select name="nxt_footer_cta" id="nxt_footer_cta"><option value="optin">Newsletter-Anmeldung</option><option value="form" selected="true">Kontaktformular</option></select>';
	} else {
		echo '<select name="nxt_footer_cta" id="nxt_footer_cta"><option value="optin">Newsletter-Anmeldung</option><option value="form">Kontaktformular</option></select>';
	}
}

// Save value of Metabox
function save_nxt_custom_footer_cta($post_id) {
	// check nonce to avoid hacker shit
	if (!isset($_POST["nxt-custom-footer-metabox-nonce"]) || !wp_verify_nonce($_POST["nxt-custom-footer-metabox-nonce"], basename(__FILE__))) return $post_id; // else echo "<!-- debug - did not make it through nonce check! -->";
	
	// check permissions of user
	if(!current_user_can("edit_post", $post_id)) return $post_id;
	
	// make sure this isn't an auto-save
	if(defined("DOING_AUTOSAVE") && DOING_AUTOSAVE) return $post_id;

	// echo "<!-- debug - this is not an autosave -->";
	// make sure this is only being displayed for pages
	$slug = "page";
	if( $slug != get_post_type($post_id)) return $post_id;
	if((isset($_POST["nxt_footer_cta"])) && ($_POST["nxt_footer_cta"] <> 'optin' )) {
		// echo "<!-- debug - nxt_second_author is set in POST variable - value: " . $_POST['nxt_second_author'] . " -->";
		update_post_meta($post_id, "_nxt_footer_cta", $_POST["nxt_footer_cta"]);
	} else {
		delete_post_meta($post_id, "_nxt_footer_cta");
	}
}
add_action('save_post', 'save_nxt_custom_footer_cta', 10, 3);