<?php
$param = [
  'product_id' => true, 
  'product_num' => true, 
  'status' => true
];

$data_form = [];
foreach ($param as $key => $value) {
  if($value && !isset($_POST[$key])) {
    $rc = 1;
    return false;
  }else {
    $data_form[$key] = $_POST[$key];
  }
}

$current_user = wp_get_current_user();
$current_id = $current_user->ID;
if($current_id == 0) {
  $rc = 1;
  return false;
}else {
  $data_form['uid'] = $current_id;
}

//檢查是否存在
$cart_res = $wpdb->get_results($wpdb->prepare("SELECT * from food_cart where `uid` = %d and `status` = 1 and `product_id` = %d", $current_id, $_POST['product_id']));
if(count($cart_res) > 0) {
  $rc = 3;
}else {
  $res = $wpdb->insert('food_cart', $data_form);
}