Adding h4 in Woocommerce attribute and custom field list - php

Question

I am displaying several product attributes and custom meta fields on the single product page with this code I got here:
function action_woocommerce_single_product_summary() {
global $product;
$attributes_names = array( 'Brand', 'Color', 'Size' );
$attributes_data = array();
foreach ( $attributes_names as $attribute_name ) {
if ( $value = $product->get_attribute($attribute_name) ) {
$attributes_data[] = $attribute_name . ': ' . $value;
}
}
// NOT empty
if ( ! empty($attributes_data) ) {
echo '<h4>' . __( 'Details', 'woocommerce' ) . '</h4><ul><li>' . implode( '</li><li>', $attributes_data );
}
// Get meta
$sn = $product->get_meta( 'Serial_Number' );
$mpn = $product->get_meta( 'MPN' );
// NOT empty
if ( ! empty ( $sn ) ) {
echo '<li>' . __( 'My label 1: ', 'woocommerce' ) . $sn . '</li>';
}
// NOT empty
if ( ! empty ( $mpn ) ) {
echo '<li>' . __( 'My label 2: ', 'woocommerce' ) . $mpn . '</li>';
}
echo '</ul>';
}
add_action( 'woocommerce_single_product_summary', 'action_woocommerce_single_product_summary', 36, 0 );
My problem is that the h4 ('Details') and the starting ul are only displayed when there are attributes. When there are only custom fields set for a product, the h4 and the starting ul for the list are not displayed. How can I always show the h4 and the starting whenever either an attribute or a custom field is set for a product?
EDIT to clarify: There are 3 possible product types:
products that have attributes AND custom fields
products that ONLY have an attribute OR custom field
products that neither have an attribute or custom field
For the first type of products, it should be displayed for example:
<h4>Details</h4>
<ul>
<li>Brand: ...</li>
<li>MPN: ...</li>
</ul>
For the second type of products an example would be:
<h4>Details</h4>
<ul>
<li>MPN: ...</li>
</ul>
and for the last type of products NOTHING should be displayed at all.

Answer 1

There are multiple ways to set that up, you could do that using either if/else statement or a ternary operator. For example you could do something like this:
// Using "if/else" method
if ( ! empty($attributes_data) ) {
echo '<h4>' . __( 'Details', 'woocommerce' ) . '</h4><ul><li>' . implode( '</li><li>', $attributes_data );
}else{
// if it's empty you could output a placeholder text OR a any value you could get from woocommerce
echo '<h4>' . __( 'Details', 'woocommerce' ) . '</h4><span>' . {YOUR VALUE OR PLACEHOLDER TEXT AS A FALLBACK} . '</span>';
}
Or you could use the ternary operator like so:
echo ( ! empty($attributes_data) ) ? '<h4>' . __( 'Details', 'woocommerce' ) . '</h4><ul><li>' . implode( '</li><li>', $attributes_data ) : '<h4>' . __( 'Details', 'woocommerce' ) . '</h4><span>' . {YOUR VALUE OR PLACEHOLDER TEXT AS A FALLBACK} . '</span>';
EDIT
Assuming that Serial_Number and MPN are your custom fields, you could set your if condition like this:
add_action( 'woocommerce_single_product_summary', 'action_woocommerce_single_product_summary', 36, 0 );
function action_woocommerce_single_product_summary()
{
global $product;
$attributes_names = array( 'Brand', 'Color', 'Size' );
$attributes_data = array();
foreach ( $attributes_names as $attribute_name ) {
if ( $value = $product->get_attribute($attribute_name) ) {
$attributes_data[] = $attribute_name . ': ' . $value;
}
}
$sn = $product->get_meta( 'Serial_Number' );
$mpn = $product->get_meta( 'MPN' );
// Assuming that 'Serial_Number' and 'MPN' are your custom fields
if(! empty($attributes_data) && ! empty ( $sn ) && ! empty ( $mpn )){
echo '<h4>' . __( 'Details', 'woocommerce' ) . '</h4><ul><li>' . implode( '</li><li>', $attributes_data );
echo '<li>' . __( 'My label 1: ', 'woocommerce' ) . $sn . '</li>';
echo '<li>' . __( 'My label 2: ', 'woocommerce' ) . $mpn . '</li>';
echo '</ul>';
}elseif(! empty($attributes_data) || ! empty ( $sn ) || ! empty ( $mpn )){
echo ( ! empty($attributes_data)) ? '<h4>' . __( 'Details', 'woocommerce' ) . '</h4><ul><li>' . implode( '</li><li>', $attributes_data ): '<h4>' . __( 'Details', 'woocommerce' ) . '</h4><ul>';
echo (! empty ( $sn )) ? '<li>' . __( 'My label 1: ', 'woocommerce' ) . $sn . '</li>' : "";
echo (! empty ( $mpn )) ? '<li>' . __( 'My label 2: ', 'woocommerce' ) . $mpn . '</li>': "";
echo '</ul>';
}else{
echo '<h4>' . __( 'Details', 'woocommerce' ) . '</h4><p>Looks like there is no extra info on this product!</p>';
}
}
Let me know if that is what you're looking for!