php-PHP关于数组返回值显示为空

if ($jsonArrayData['issuccessful']) {
$requestData = [
'venderId' => (int)$venderid,
'address' => urlencode($address['addressDetail']),
'daType' => 0,
'pickuptime' =>"",
];
想让这段代码最后一个值显示为空，但是如果删掉 'pickuptime' =>"",就会显示密码错误， 使用NULL的话就会显示即时时间。怎么让 'pickuptime' 显示为空？