How to control json_encode behavior? - php

Question

Is there any way to control json_encode behavior on objects? Like excluding empty arrays, null fields and so on?
I mean something like when using serialize(), where you can implement magic __sleep() method and specify what properties should be serialized:
class MyClass
{
public $yes = "I should be encoded/serialized!";
public $empty = array(); // // Do not encode me!
public $null = null; // Do not encode me!
public function __sleep() { return array('yes'); }
}
$obj = new MyClass();
var_dump(json_encode($obj));

Answer 1

The most correct solution is extending the interface JsonSerializable;
by using this interface you just need to return with the function jsonSerialize() what you want json_encode to encode instead of your class.
Using your example:
class MyClass implements JsonSerializable{
public $yes = "I should be encoded/serialized!";
public $empty = array(); // // Do not encode me!
public $null = null; // Do not encode me!
function jsonSerialize() {
return Array('yes'=>$this->yes);// Encode this array instead of the current element
}
public function __sleep() { return array('yes'); }//this works with serialize()
}
$obj = new MyClass();
echo json_encode($obj); //This should return {yes:"I should be encoded/serialized!"}
Note: this works in php >= 5.4 http://php.net/manual/en/class.jsonserializable.php

Answer 2

You could make the variables private. Then they won't show up in the JSON encoding.
If that is not an option, you could make a private array, and use the magic methods __get($key) and __set($key,$value) to set and get values in/from this array. In your case the keys would be 'empty' and 'null'. You can then still access them publicly but the JSON encoder will not find them.
class A
{
public $yes = "...";
private $privateVars = array();
public function __get($key)
{
if (array_key_exists($key, $this->privateVars))
return $this->privateVars[$key];
return null;
}
public function __set($key, $value)
{
$this->privateVars[$key] = $value;
}
}
http://www.php.net/manual/en/language.oop5.overloading.php#object.get