add_action('woocommerce_after_shop_loop_item', 'wc_whatsapp_button', 10 );
add_action('woocommerce_after_add_to_cart_button', 'wc_whatsapp_button', 10 );
function wc_whatsapp_button() {
    global $product;
    $button_text = 'WhatsApp';
    $phone = '905555555555';
    $text = urlencode($product->get_title().' Ürünü için yazıyorum');
    echo '<a target="_blank" class="btn btn-success" href="https://wa.me/'.$phone.'?text='.$text.'">WhatsApp</a>';
}

function woocommerce_template_loop_add_to_cart(){return wc_whatsapp_button();}
function woocommerce_template_single_add_to_cart(){return wc_whatsapp_button();}
function wc_whatsapp_button() {
    global $product;
    $button_text = 'WhatsApp';
    $phone = '905555555555';
    $text = urlencode($product->get_title().' Ürünü için yazıyorum');
    echo '<a target="_blank" class="btn btn-success" href="https://wa.me/'.$phone.'?text='.$text.'">WhatsApp</a>';
}