PHP - json_encode不打印对象

Question

我有两个类ServiceDetails和AvailableServices

class ServiceDetails { 
    private $service_name; 
    private $price; 
    private $currency_id; 
    public function __construct($service_name, $price, $currency_id) { 
     $this->service_name = $service_name; 
     $this->price = $price; 
     $this->currency_id = $currency_id; 
    } 
} 

class AvailableServices { 
    public $services; 
    public function __construct() { 
     $this->services = []; 
    } 
} 

我创建的AvailableServices一个实例，并加入ServiceDetails类的一个对象到$services阵列AvailableServices实例。

$services = new AvailableServices(); 
$service_details = new ServiceDetails($a, $b, $c); 
$services->services[] = clone $service_details; 

我var_dump的$services对象，并将其正确输出。然而，当我做json_encode，除外AvailableServices的services财产没有输出。

var_dump($services); // something 
echo json_encode($services); // nothing 

Answer 1

对于json_encode打印出来的属性，这些属性必须是public。更改ServiceDetails使用public代替private解决了问题。

class ServiceDetails { 
    public $service_name; 
    public $price; 
    public $currency_id; 
    public function __construct($service_name, $price, $currency_id) { 
     $this->service_name = $service_name; 
     $this->price = $price; 
     $this->currency_id = $currency_id; 
    } 
} 

Answer 2

正确答案这里是实现JsonSerializable接口ServiceDetails类。

class ServiceDetails implements JsonSerializable{ 
    private $service_name; 
    private $price; 
    private $currency_id; 
    public function __construct($service_name, $price, $currency_id) { 
     $this->service_name = $service_name; 
     $this->price = $price; 
     $this->currency_id = $currency_id; 
    } 

    /** 
    * Returns JSON representation 
    * 
    * @return array|mixed 
    */ 
    public function jsonSerialize() { 
     return get_object_vars($this); 
    }  
}