如何利用php语法将数组转化成json数据

$data = array(
  'name' => '小米',
  'age' => 22,
  'gender' => '男'
);
$json_data = json_encode($data);

//输出结果：
{
  "name": "小米",
  "age": 20,
  "gender": "男"
}