WooCommerce add notices for when backorders are (not) allowed.

woocommerce-show-notice-when-backorder.php

//output with add to cart button on product detail page
add_action( 'woocommerce_after_add_to_cart_form', 'custom_notice_for_backorders_allowed' );

function custom_notice_for_backorders_allowed() 
	{
		//instantinate product object
		global $product;
        
        //check if backorders are allowed
		if ( $product->backorders_allowed() ) 
  	 	{
			?>
			Backorders allowed: Put some text and <a href="#">links here.</a>
			<?php
		}
		
	}


//output after product title
add_action( 'woocommerce_single_product_summary', 'custom_notice_for_backorders_not_allowed' );

function custom_notice_for_backorders_not_allowed() 
	{
		global $product;
        
        //check if backorders are not allowed
		if ( ! $product->backorders_allowed() ) 
  	 	{	
  	 		?>
			Backorders not allowed: Put some text and <a href="#">links here.</a>
			<?php
		}
		
	}