add_action("wp_ajax_custom_function", "my_custom_function");
add_action("wp_ajax_nopriv_custom_function", "my_custom_function");
function my_custom_function()
{
global $wpdb;

$name = isset($_POST["DescricaoProd"]) ? $_POST["DescricaoProd"] : '';
$unid = isset($_POST["DescricaoUnid"]) ? $_POST["DescricaoUnid"] : '';

if (!empty($name) && !empty($unid)) {
echo json_encode("true");
} else {
echo json_encode("false");
}

$servername = "xxx.xxx.x.xx";
$username = "xxxxx";
$password = "xxxxxx";
$dbname = "xxxxxxx";
$conn = new mysqli($servername, $username, $password, $dbname);
$conn->set_charset('utf8');

$conn->insert(
'ProdHigieneteste',
array(
'DescricaoProd' => $name,
'DescricaoUnid' => $unid
),
array(
'%s',
'%d'
)
);

$conn->insert(
'StockHigieneteste',
array(
'DescricaoProd' => $name,
'DescricaoUnid' => $unid
),
array(
'%s',
'%d'
)
);
wp_die();
}