Missing required param: interval - stripe/PHP - php

Question

I don't understand what going on my stripe code on PHP. I Certainly Definition interval but They are tell me "Missing required param: interval"
I just want to make a plan object.I want to create a plan object after creating a Customer object from the token received from ajax as below.
Is it necessary to obtain another php external resource from Composer etc. to make a plan?
I made a plan as follows
\Stripe\Plan::create();
// \Stripe\Stripe::setApiKey("sk_test_");
$plan = \Stripe\Plan::create(array(
"amount" => 5000,
"interval" => "month",
"product" => array(
"name" => "Emerald classic"
),
"currency" => "jpy",
"id" => "emerald-classic"
));
All sources are this
<?php
header("Content-type: text/plain; charset=UTF-8");
if(isset($_SERVER['HTTP_X_REQUESTED_WITH'])
&& strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest')
{
if (isset($_POST['request']))
{
$name = $_POST['request'];
require_once 'vendor/autoload.php';
\Stripe\Stripe::setApiKey("sk_test_");
\Stripe\Customer::create();
$customer = \Stripe\Customer::create(array(
"description" => "taylor#example.com",
"source" => "$name",
));
//echo $customer;
$customer_array = $customer->__toArray(true);
foreach ($customer_array as $key => $value) {
if ($key === "id") {
$value_cus = $value;
}
}
echo $value_cus;
\Stripe\Plan::create();
// \Stripe\Stripe::setApiKey("sk_test_");
$plan = \Stripe\Plan::create(array(
"amount" => 5000,
"interval" => "month",
"product" => array(
"name" => "Emerald classic"
),
"currency" => "jpy",
"id" => "emerald-classic"
));
};
};
?>