Replace displayed product zero price by a text in WooCommerce variable products

I use the following code in WooCommerce, to replace the displayed product zero price with a custom text:

add_filter( 'woocommerce_get_price_html', 'wtwh_price_free_zero', 9999, 2 );  
function wtwh_price_free_zero( $price, $product ) {
    if ( $product->is_type( 'variable' ) ) {
        $prices = $product->get_variation_prices( true );
        $min_price = current( $prices['price'] );
        if ( 0 == $min_price ) {
            $max_price = end( $prices['price'] );
            $min_reg_price = current( $prices['regular_price'] );
            $max_reg_price = end( $prices['regular_price'] );
            if ( $min_price !== $max_price ) {
                $price = wc_format_price_range( 'FREE', $max_price );
                $price .= $product->get_price_suffix();
            } elseif ( $product->is_on_sale() && $min_reg_price === $max_reg_price ) {
                $price = wc_format_sale_price( wc_price( $max_reg_price ), 'FREE' );
                $price .= $product->get_price_suffix();
            } else {
                $price = 'FREE';
            }
        }
    } elseif ( 0 == $product->get_price() ) {
        $price = '<span class="woocommerce-Price-amount amount">Contact us for a unique quote!</span>';
    }  
    return $price;
}

The problem is that this doesn't work for my variable products, and I would like to have a similar behavior for those variable products, replacing zero formatted price with "FREE" string.

How to replace product displayed zero price by a text for WooCommerce variable products?

Solution

You were near. You can use str_replace() PHP function to replace the zero formatted price with "FREE" string for your variable products. This way, the required code will e simpler and compact.

Try the following revised code replacement:

add_filter( 'woocommerce_get_price_html', 'custom_display_for_product_with_zero_price', 9999, 2 );
function custom_display_for_product_with_zero_price( $price_html, $product ) {
    if ( $product->is_type( 'variable' ) ) {
        // Replace any formatted zero price with "FREE" string
        $price_html = str_replace( wc_price(0), esc_html__('FREE', 'woocommerce'), $price_html ); 
    } elseif ( 0 == $product->get_price() ) {
        $price_html = sprintf(
            '<span class="woocommerce-Price-amount amount">%s</span>', 
            esc_html__('Contact us for a unique quote!', 'woocommerce')
        );
    }  
    return $price_html;
}

Now it should work for your variable product(s).