我尝试使用postman发送一些post值到我的脚本php...但是我只能打印出post值，如果我使用x-www-form-urlencoded，而不是如果我通过form-data发送数据？
这是为什么？无法理解x-www-form-urlencoded和form-data之间的差异。

php代码测试：

<?php
// this script call to register new user into db
require ("../private/index.php");
if ($_SERVER['REQUEST_METHOD'] == "POST") {
    $staff = $_POST['staff_ID'];
    $email = $_POST['email'];
    $pass = $_POST['password'];
    $name = $_POST['Name'];
    $surname = $_POST['Surname'];
    $role = $_POST['Role'];
    $instructor = $_POST['Instructor'];
    $date = $date = date("Y-m-d H:i:s",time());
    $dataReceived = array('staff_ID'=>$staff,
    'email'=>$email,
    'password'=>$pass,
    'Name'=>$name,
    'Surname'=>$surname,
    'Role'=>$role);
    echo json_encode($dataReceived);
   $sql = "INSERT INTO `users_nx`(`staff_ID`,`password`,`email`,`Name`,`Surname`,`Role`) VALUES ($staff,$pass,$email,$name,$surname,$role)";
   if ($mysqli->query($sql) === TRUE) {
    echo resultOperations(true, $mysqli);
    } else {
    echo resultOperations(false,$mysqli);
    }
}