validate length billing phone and shipping phone woocommerce

validate-length-billing-phone-and-shipping-phone-woocommerce.php

add_action('woocommerce_checkout_process', 'check_phone_number_length');
function check_phone_number_length() {
    global $woocommerce;
    if ( ! (preg_match('/^[0-9]{10}$/D', $_POST['billing_phone'] ))){
        wc_add_notice( "<strong>Telefon facturare</strong> Număr incorect ! Trebuie să conțină 10 cifre"  ,'error' );
    }
    if (isset($_POST['shipping_phone']) && !empty($_POST['shipping_phone'])) {
      if ( ! (preg_match('/^[0-9]{10}$/D', $_POST['shipping_phone'] ))){
        wc_add_notice( "<strong>Telefon livrare</strong> Număr incorect ! Trebuie să conțină 10 cifre"  ,'error' );
      }
    }
}