Reference
In This Article
Advanced Usage
JSON Objects
When encoding PHP objects as JSON, all public properties of that object will be encoded in a JSON object.
JSON does not allow object references, so care should be taken not to encode
objects with recursive references. If you have issues with recursion,
Zend\Json\Json::encode()
and Zend\Json\Encoder::encode()
each allow an
optional second parameter to check for recursion; if an object is serialized
twice, an exception will be thrown.
Decoding JSON objects poses additional difficulty, however, since JavaScript objects correspond most closely to PHP's associative array. Some suggest that a class identifier should be passed, and an object instance of that class should be created and populated with the key/value pairs of the JSON object; others feel this could pose a substantial security risk.
By default, Zend\Json\Json
will decode JSON objects as stdClass
objects.
However, if you desire an associative array returned, you can request it using
the second argument to decode()
:
// Decode JSON objects as PHP array
$phpNative = Zend\Json\Json::decode($encodedValue, Zend\Json\Json::TYPE_ARRAY);
Any objects thus decoded are returned as associative arrays with keys and values corresponding to the key/value pairs in the JSON notation.
The recommendation of Zend Framework is that the individual developer should decide how to decode JSON objects. If an object of a specified type should be created, it can be created in the developer code and populated with the values decoded using zend-json.
Encoding PHP Objects
If you are encoding PHP objects, the default encoding mechanism can only
access public properties of these objects. When a method toJson()
is
implemented on an object to encode, Zend\Json\Json
calls this method and
expects the object to return a JSON representation of its internal state.
Zend\Json\Json
can encode PHP objects recursively but does not do so by
default. This can be enabled by passing true
as the second argument to
Zend\Json\Json::encode()
.
// Encode PHP object recursively
$jsonObject = Zend\Json\Json::encode($data, true);
When doing recursive encoding of objects, as JSON does not support cycles, a
Zend\Json\Exception\RecursionException
will be thrown. If you wish, you can
silence these exceptions by passing the silenceCyclicalExceptions
option:
$jsonObject = Zend\Json\Json::encode(
$data,
true,
['silenceCyclicalExceptions' => true]
);
Internal Encoder/Decoder
Zend\Json
has two different modes depending if ext/json is enabled in your PHP
installation or not. If ext/json
is installed, zend-json will use the
json_encode()
and json_decode()
functions for encoding and decoding JSON. If
ext/json
is not installed, a Zend Framework implementation in PHP code is used
for en/decoding. This is considerably slower than using the PHP extension, but
behaves exactly the same.
Sometimes you might want to use the zend-json encoder/decoder even if you have
ext/json
installed. You can achieve this by calling:
Zend\Json\Json::$useBuiltinEncoderDecoder = true;
JSON Expressions
JavaScript makes heavy use of anonymous function callbacks, which can be saved
within JSON object variables. They only work if not returned inside double
quotes, which zend-json implements by default. With the Expression support for
zend-json, you can encode JSON objects with valid JavaScript callbacks.
This works when either json_encode()
or the internal encoder is used.
A JavaScript callback is represented using the Zend\Json\Expr
object. It
implements the value object pattern and is immutable. You can set the JavaScript
expression as the first constructor argument. By default
Zend\Json\Json::encode()
does not encode JavaScript callbacks; you have to
pass the option enableJsonExprFinder
and set it to TRUE
when calling the
encode()
method. If enabled, the expression support works for all nested
expressions in large object structures.
As an example:
$data = [
'onClick' => new Zend\Json\Expr(
'function() {'
. 'alert("I am a valid JavaScript callback created by Zend\\Json");
. '}'
),
'other' => 'no expression',
];
$jsonObjectWithExpression = Zend\Json\Json::encode(
$data,
false,
['enableJsonExprFinder' => true]
);
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