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    JsonSerializable::jsonSerialize

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

    JsonSerializable::jsonSerialize — JSON にシリアライズしたいデータを指定する

    説明

    public JsonSerializable::jsonSerialize(): mixed

    オブジェクトをシリアライズして、 json_encode() がネイティブにシリアライズできる値にします。

    パラメータ

    この関数にはパラメータはありません。

    戻り値

    json_encode() でシリアライズするデータを返します。 resource 型以外の任意の型になります。

    例

    例1 JsonSerializable::jsonSerialize() で配列を返す例

    <?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);
    ?>

    上の例の出力は以下となります。

    [
    1,
    2,
    3
]

    例2 JsonSerializable::jsonSerialize() で連想配列を返す例

    <?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);
    ?>

    上の例の出力は以下となります。

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

    例3 JsonSerializable::jsonSerialize() で整数値を返す例

    <?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);
    ?>

    上の例の出力は以下となります。

    1

    例4 JsonSerializable::jsonSerialize() で文字列を返す例

    <?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);
    ?>

    上の例の出力は以下となります。

    "Hello!"

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    User Contributed Notes 4 notes

    up
    78
    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"}

    ?>
    up
    17
    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))
    ])
    );

    ?>
    up
    5
    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}
    up
    1
    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
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