php代码返回空白页面

Question

我正在测试本地wordpress网站的一些代码，并正在编辑主题的functions.php文件。当我写下面的代码时，它只返回一个空白站点。谁能开导我？我尝试打开W​​AMP的错误报告，但没有出现。

global $woocommerce;
$box_found = false;
$voucher_found = false;
$other_products_found = false;

//start of the loop that fetches the cart items
foreach($woocommerce->cart->get_cart() as $cart_item_key => $values ) {
    $_product = $values['data'];
    $terms = get_the_terms( $_product->id, 'product_cat' );

    // second level loop search, in case some items have several categories
    foreach ($terms as $term) {
        $_categoryid = $term->term_id;
    }

    //check if BOX product category is in card
    if ( $_categoryid === 103 ) {
        //category is in cart!
        $box_found = true;
    }

    //check if VOUCHER product category is in card
    if ( $_categoryid === 106 ) {
        //category is in cart!
        $voucher_found = true;
    }

    //check if VOUCHER product category is in card
    if (( $_categoryid !== 103 )||($_categoryid !== 106 )) {
        //category is in cart!
        $other_products_found = true;
    }
}

但是，当我将整个代码包含在函数中时，网页将恢复正常。