Woocommerce: Display custom labels for products in selected categories (e.g., "New In", "Flash Sale")

edm-product-custom-labels.php

<?php
/**
 * Display custom labels for products in selected categories
 *
 * @param array $labels Array labels
 *
 * - Instructions -
 * 1) Create a product category 'Flash Sale'
 * 2) Assign products to that category
 *  
 * If you want a label for other categories, 
 * change the first argument of the 'has_term' function
 * to the name of the category you want.
 * Duplicate the entire 'if' statement and change the argument accordingly
 * to insert more labels
 */
 
 function edm_render_custom_labels( $labels ) {
	//if there are no labels, exit function
	if ( !count( $labels ) ) {
		return;
	}
	?>	
	<div class="custom-labels">
		<ul>
        	<?php foreach( $labels as $label ) { ?>
			<li class="custom-label <?php echo $label['class'];?> "><?php echo $label['name']; ?></li>
		<?php } ?>
		</ul>
	</div>
	<?php
}

function edm_add_custom_labels() {
	global $product;
	//create an array to store labels
	$labels = array();
	//get stock status
	$status = get_post_meta($product->get_id(), '_stock_status', true);
	
	//'Flash Sale' Label. Check if product is in a category with the slug name 'flash-sale'
	if ( has_term('Flash Sale', 'product_cat') ) {
		$labels['sale'] = array(
			'name' 	=> 'Flash Sale',
			'class' => 'flash-sale',
		);
	}
	
	//New In label. Check if product is in a category with the slug name 'new-in'
	if ( has_term('new-in', 'product_cat') ) {
		$labels['new'] = array(
			'name' 	=> 'New In',
			'class' => 'new-in',
		);
	}
	
	//Out of stock label
	if ( $status === 'outofstock' ) {
		$labels['soldout'] = array(
			'name'	=> 'Sold Out',
			'class' => 'sold-out'
		);
	}
	
	//Display labels
	edm_render_custom_labels( $labels );
}
add_action( 'woocommerce_shop_loop_item_title', 'edm_add_custom_labels', 5 );
add_action( 'woocommerce_single_product_summary', 'edm_add_custom_labels' );