JsonSerializable::jsonSerialize

(PHP 5 >= 5.4.0, PHP 7, PHP 8)

JsonSerializable::jsonSerialize — Specify data which should be serialized to JSON

Description

public JsonSerializable::jsonSerialize(): mixed

Serializes the object to a value that can be serialized natively by json_encode().

Parameters

This function has no parameters.

Return Values

Returns data which can be serialized by json_encode(), which is a value of any type other than a resource.

Examples

Example #1 JsonSerializable::jsonSerialize() example returning an array

<?php
class ArrayValue implements JsonSerializable {
    private $array;
    public function __construct(array $array) {
        $this->array = $array;
    }

    public function jsonSerialize(): mixed {
        return $this->array;
    }
}

$array = [1, 2, 3];
echo json_encode(new ArrayValue($array), JSON_PRETTY_PRINT);
?>

The above example will output:

Example #2 JsonSerializable::jsonSerialize() example returning an associative array

<?php
class ArrayValue implements JsonSerializable {
    private $array;
    public function __construct(array $array) {
        $this->array = $array;
    }

    public function jsonSerialize() {
        return $this->array;
    }
}

$array = ['foo' => 'bar', 'quux' => 'baz'];
echo json_encode(new ArrayValue($array), JSON_PRETTY_PRINT);
?>

The above example will output:

{
    "foo": "bar",
    "quux": "baz"
}

Example #3 JsonSerializable::jsonSerialize() example returning an int

<?php
class IntegerValue implements JsonSerializable {
    private $number;
    public function __construct($number) {
        $this->number = (int) $number;
    }

    public function jsonSerialize() {
        return $this->number;
    }
}

echo json_encode(new IntegerValue(1), JSON_PRETTY_PRINT);
?>

The above example will output:

Example #4 JsonSerializable::jsonSerialize() example returning a string

<?php
class StringValue implements JsonSerializable {
    private $string;
    public function __construct($string) {
        $this->string = (string) $string;
    }

    public function jsonSerialize() {
        return $this->string;
    }
}

echo json_encode(new StringValue('Hello!'), JSON_PRETTY_PRINT);
?>

The above example will output:

"Hello!"

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User Contributed Notes 5 notes

down

benkuhl at gmail dot com ¶

11 years ago

A good example on when you would use functionality like this is when working with objects.

json_encode() will take a DateTime and convert it to:

{
    "date":"2013-01-31 11:14:05",
    "timezone_type":3,
    "timezone":"America\/Los_Angeles"
}

This is great when working with PHP, but if the Date is being read by Java.  The Java date parser doesn't know what to do with that.  But it does know what to do with the ISO8601 format...

<?php

date_default_timezone_set('America/Los_Angeles');

class Fruit implements JsonSerializable {
    public
        $type = 'Apple',
        $lastEaten = null;

    public function __construct() {
        $this->lastEaten = new DateTime();
    }

    public function jsonSerialize() {
        return [
            'type' => $this->type,
            'lastEaten' => $this->lastEaten->format(DateTime::ISO8601)
        ];
    }
}
echo json_encode(new Fruit()); //which outputs: {"type":"Apple","lastEaten":"2013-01-31T11:17:07-0500"}

?>

down

tomasz dot darmetko at gmail dot com ¶

7 years ago

Nested json serializable objects will be serialized recursively. No need to call ->jsonSerialize() on your own. It is especially useful in collections.

<?php

class NestedSerializable implements \JsonSerializable
{

    private $serializable;

    public function __construct($serializable)
    {
        $this->serializable = $serializable;
    }

    public function jsonSerialize()
    {
        return [
            'serialized' => $this->serializable
        ];
    }

}

class SerializableCollection implements \JsonSerializable {

    private $elements;

    public function __construct(array $elements)
    {
        $this->elements = $elements;
    }

    public function jsonSerialize()
    {
        return $this->elements;
    }

}

// Outputs: [{"serialized":null},{"serialized":null},{"serialized":{"serialized":null}}]
echo json_encode(
    new SerializableCollection([
        new NestedSerializable(null),
        new NestedSerializable(null),
        new NestedSerializable(new NestedSerializable(null))
    ])
);

?>

down

info at digistratum dot com ¶

7 years ago

Here's a small test/proof that makes it easy to see some comparative results. Null was the one I was interested in since it was not documented:

<?php
class jsontest implements JsonSerializable {
        function __construct($value) { $this->value = $value; }
        function jsonSerialize() { return $this->value; }
}

print "Null -> " . json_encode(new jsontest(null)) . "\n";
print "Array -> " . json_encode(new jsontest(Array(1,2,3))) . "\n";
print "Assoc. -> " . json_encode(new jsontest(Array('a'=>1,'b'=>3,'c'=>4))) . "\n";
print "Int -> " . json_encode(new jsontest(5)) . "\n";
print "String -> " . json_encode(new jsontest('Hello, World!')) . "\n";
print "Object -> " . json_encode(new jsontest((object) Array('a'=>1,'b'=>3,'c'=>4))) . "\n";
?>

Output is:
Null -> null
Array -> [1,2,3]
Assoc. -> {"a":1,"b":3,"c":4}
Int -> 5
String -> "Hello, World!"
Object -> {"a":1,"b":3,"c":4}

down

david at vanlaatum dot id dot au ¶

9 years ago

simonsimcity at gmail dot com is wrong, you can throw exceptions in this but it will wrap with another exception so his example outputs

 PHP Fatal error:  Uncaught exception 'RuntimeException' with message 'It failed!' in -:8
 Stack trace:
 #0 [internal function]: Foo->jsonSerialize()
 #1 -(16): json_encode(Object(Foo))
 #2 {main}

 Next exception 'Exception' with message 'Failed calling Foo::jsonSerialize()' in -:16
 Stack trace:
 #0 -(0): json_encode()
 #1 {main}
   thrown in - on line 16

PHP 5.4.39

down

-5

rmdundon at gmail dot com ¶

5 years ago

For those who are also lazy. You cannot just include $this and expect it to work.

For example, this won't work:

<?php
class SomeClass implements JsonSerializable {
 
   protected $partner;

   function setPartner(object $partner) {
       $this->partner;
   }

   public function jsonSerialize() {
        return $this;
    }
}

$foo = new SomeClass();
$too = new stdClass();
$too->test = 1;
$foo->setPartner = $too;

echo json_encode($foo); // Shows a blank object "{}"

?>

You have to define the things manually, so this will work.

<?php
class SomeClass implements JsonSerializable {
 
   protected $partner;

   function setPartner(object $partner) {
       $this->partner;
   }

   public function jsonSerialize() {
        $data['partner'] = $this->partner;
        return $data;
    }
}

$foo = new SomeClass();
$too = new stdClass();
$too->test = 1;
$foo->setPartner = $too;

echo json_encode($foo); // Shows {"partner":{"test":1}}

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