Replace zero with FREE for WooCommerce shipping rates on single product page

Question

Based on the answer on my previous question, Issue display shipping data on WooCommerce single product page, I'm trying to replace the 0 with FREE or whatever word I choose.

Problem is, whatever I do, it does not work. This is my attempt and I need help with it:

add_action('woocommerce_after_add_to_cart_form', 'display_shipping_on_product_page', 10, 0);
function display_shipping_on_product_page(){

    // get all zones
    $zones = WC_Shipping_Zones::get_zones();

    // get the shop base country
    $base_country = WC()->countries->get_base_country();
    $base_city = WC()->countries->get_base_city();

    // start display of table
    echo '<div>' . __( '<b>Available Shipping</b>', 'woocommerce' );
    echo '<br><small><span class="shipping-time-cutoff">All orders are shipped from the '.$base_country.'. Order before 12AM Mon-Fri for same day delivery within '.$base_city.'. Order before 3PM Mon-Thu for next day delivery.</span></small>';
    echo '<small><table class="shipping-and-delivery-table">';

    // get name of each zone and each shipping method for each zone
    foreach ( $zones as $zone_id => $zone ) {
        
        echo '<tr><td>';
       
        echo '<strong>' . $zone['zone_name'] . '</strong>' . '</td><td>';

        $zone_shipping_methods = $zone['shipping_methods'];
    
        foreach ( $zone_shipping_methods as $index => $method ) {
            $instance = $method->instance_settings;
                        
            if ( isset( $instance['min_amount'] ) ) {
                $instance_min_amount = $instance['min_amount'];
            } else {
                $instance_min_amount = 0;
            }

            if ( isset( $instance['cost'] ) ) {
                $instance_cost = $instance['cost'];
            } else {
                $instance_cost = str_replace($instance_cost, "FREE" );
            }
            
            $cost = $instance_cost ? $instance_cost : $instance_min_amount;
            $above = $instance_min_amount ? 'above ' : '';
            
            echo $instance['title'] . ': ' . $above . '<strong>' . wc_price( $cost ) . '</strong>' . '<br>';
        }
        echo '</td></tr>';
    }
    echo '</table></small></div>';
}

This is what I tried to add / edit without success:

$instance_cost = str_replace($instance_cost, "FREE" );

Answer 1

To display 'free' instead of 0, you need to change your if/else conditions. Explanation via comment tags added to my answer.

So you get:

function action_woocommerce_after_add_to_cart_form() {
    // get all zones
    $zones = WC_Shipping_Zones::get_zones();

    // get the shop base country
    $base_country = WC()->countries->get_base_country();
    $base_city = WC()->countries->get_base_city();

    // start display of table
    echo '<div>' . __( 'Available Shipping', 'woocommerce' );
    echo '<br><small><span class="shipping-time-cutoff">All orders are shipped from the '.$base_country.'. Order before 12AM Mon-Fri for same day delivery within '.$base_city.'. Order before 3PM Mon-Thu for next day delivery.</span></small>';
    echo '<small><table class="shipping-and-delivery-table">';

    // get name of each zone and each shipping method for each zone
    foreach ( $zones as $zone_id => $zone ) {
        
        echo '<tr><td>';
       
        echo '<strong>' . $zone['zone_name'] . '</strong>' . '</td><td>';

        $zone_shipping_methods = $zone['shipping_methods'];
    
        foreach ( $zone_shipping_methods as $index => $method ) {
            $instance = $method->instance_settings;
            
            // Initialize
            $above = '';
            $output_cost = __( 'Free', 'woocommerce' );

            // Cost isset
            if ( isset( $instance['cost'] ) ) {
                // NOT empty
                if ( ! empty ( $instance['cost'] ) ) {
                    // Output
                    $output_cost = wc_price( $instance['cost'] );   
                }
            }
            
            // Min amount isset
            if ( isset( $instance['min_amount'] ) ) {
                // NOT empty
                if ( ! empty ( $instance['min_amount'] ) ) {
                    // Above
                    $above = __( 'above ', 'woocommerce' );
                    
                    // Output
                    $output_cost = wc_price( $instance['min_amount'] );
                }
            }
            
            echo $instance['title'] . ': ' . $above . '<strong>' . $output_cost . '</strong>' . '<br>';        
        }

        echo '</td></tr>';
    }
        
    echo '</table></small></div>';
}
add_action( 'woocommerce_after_add_to_cart_form', 'action_woocommerce_after_add_to_cart_form', 10, 0 );