预定义常量

下列常量由此扩展定义，且仅在此扩展编译入 PHP 或在运行时动态载入时可用。

以下常量表示了 json_last_error() 所返回的错误类型。

JSON_ERROR_NONE ( integer )

没有错误发生。自 PHP 5.3.0 起生效。

JSON_ERROR_DEPTH ( integer )

到达了最大堆栈深度。自 PHP 5.3.0 起生效。

JSON_ERROR_STATE_MISMATCH ( integer )

出现了下溢（underflow）或者模式不匹配。自 PHP 5.3.0 起生效。

JSON_ERROR_CTRL_CHAR ( integer )

控制字符错误，可能是编码不对。自 PHP 5.3.0 起生效。

JSON_ERROR_SYNTAX ( integer )

语法错误。自 PHP 5.3.0 起生效。

JSON_ERROR_UTF8 ( integer )

异常的 UTF-8 字符，也许是因为不正确的编码。此常量自 PHP 5.3.3 起生效。

JSON_ERROR_RECURSION ( integer )

The object or array passed to json_encode() include recursive references and cannot be encoded. If the JSON_PARTIAL_OUTPUT_ON_ERROR option was given, NULL will be encoded in the place of the recursive reference.

This constant is available as of PHP 5.5.0.

JSON_ERROR_INF_OR_NAN ( integer )

The value passed to json_encode() includes either NAN or INF . If the JSON_PARTIAL_OUTPUT_ON_ERROR option was given, 0 will be encoded in the place of these special numbers.

This constant is available as of PHP 5.5.0.

JSON_ERROR_UNSUPPORTED_TYPE ( integer )

A value of an unsupported type was given to json_encode() , such as a resource . If the JSON_PARTIAL_OUTPUT_ON_ERROR option was given, NULL will be encoded in the place of the unsupported value.

This constant is available as of PHP 5.5.0.

下面的常量可以和 json_encode() 的 form 选项结合使用。

JSON_HEX_TAG ( integer ): 所有的 < 和 > 转换成 \u003C 和 \u003E。自 PHP 5.3.0 起生效。
JSON_HEX_AMP ( integer ): 所有的 & 转换成 \u0026。自 PHP 5.3.0 起生效。
JSON_HEX_APOS ( integer ): 所有的 ' 转换成 \u0027。自 PHP 5.3.0 起生效。
JSON_HEX_QUOT ( integer ): 所有的 " 转换成 \u0022。自 PHP 5.3.0 起生效。
JSON_FORCE_OBJECT ( integer ): 使一个非关联数组输出一个类（Object）而非数组。在数组为空而接受者需要一个类（Object）的时候尤其有用。自 PHP 5.3.0 起生效。
JSON_NUMERIC_CHECK ( integer ): 将所有数字字符串编码成数字（numbers）。自 PHP 5.3.3 起生效。
JSON_BIGINT_AS_STRING ( integer ): 将大数字编码成原始字符原来的值。自 PHP 5.4.0 起生效。
JSON_PRETTY_PRINT ( integer ): 用空白字符格式化返回的数据。自 PHP 5.4.0 起生效。
JSON_UNESCAPED_SLASHES ( integer ): 不要编码 /。自 PHP 5.4.0 起生效。
JSON_UNESCAPED_UNICODE ( integer ): 以字面编码多字节 Unicode 字符（默认是编码成 \uXXXX）。自 PHP 5.4.0 起生效。

用户评论:

[#1] JuanP [2015-11-24 13:42:08]

Updated format values list:

JSON_HEX_TAG => 1
JSON_HEX_AMP => 2
JSON_HEX_APOS => 4
JSON_HEX_QUOT => 8
JSON_FORCE_OBJECT => 16
JSON_NUMERIC_CHECK => 32
JSON_UNESCAPED_SLASHES => 64
JSON_PRETTY_PRINT => 128
JSON_UNESCAPED_UNICODE => 256
JSON_PARTIAL_OUTPUT_ON_ERROR => 512
JSON_PRESERVE_ZERO_FRACTION => 1024

[#2] e dot grinec at gmail dot com [2015-09-10 04:50:16]

Please, add a constant JSON_FORCE_ARRAY, for associative array force to just array (without keys of array).

[#3] Anonymous [2015-06-13 19:58:59]

I am working with "Marathi Language Data" and I found that when I encoded Marathi data to json using json_encode it returned me unicode values of each character like below:

Program :

<?php $ar = array("word" => "????"); echo json_encode($ar); ?>

Output of program is :

{"word":"\u0927\u093e\u0921\u0938"}

This is not expected output because what I need is output as

{"word":"????"}

So I used following code:

<?php $ar = array("word" => "????"); echo json_encode($ar, JSON_UNESCAPED_UNICODE); ?>

And I got the required output as :

{"word":"????"}

[#4] on5wis at mac dot com [2015-04-24 09:27:24]

since json_encode expects a UTF-8 string there is no need to encode the ? symbol.

I suggest you try to echo : json_encode('?');
It gives: "\u20ac"
I'm running PHP 5.6.5 on the CLI, on MacOS X 10.10

[#5] jgarviahonrado at yahoo dot es [2015-04-17 10:06:52]

When decoding the euro symbol (?) as below:

json_encode(utf8_encode('?')

json_encode provides the UTF-8 code \u0080, but it would be really interesting to get the \u20AC one.

Maybe a new option could be added to get the current code or the \u20AC one.

[#6] Yzmir Ramirez [2014-09-23 00:31:53]

If you curious of the numeric values of the constants, as of JSON 1.2.1, the constants have the following values (not that you should use the numbers directly):

JSON_HEX_TAG => 1
JSON_HEX_AMP => 2
JSON_HEX_APOS => 4
JSON_HEX_QUOT => 8
JSON_FORCE_OBJECT => 16
JSON_NUMERIC_CHECK => 32
JSON_UNESCAPED_SLASHES => 64
JSON_PRETTY_PRINT => 128
JSON_UNESCAPED_UNICODE => 256

JSON_ERROR_DEPTH => 1
JSON_ERROR_STATE_MISMATCH => 2
JSON_ERROR_CTRL_CHAR => 3

JSON_ERROR_SYNTAX => 4

JSON_ERROR_UTF8 => 5
JSON_OBJECT_AS_ARRAY => 1

JSON_BIGINT_AS_STRING => 2