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。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. Available since 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. Available since 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. Available since PHP 5.5.0.
JSON_ERROR_INVALID_PROPERTY_NAME (integer): A key starting with \u0000 character was in the string passed to json_decode() when decoding a JSON object into a PHP object. Available since PHP 7.0.0.
JSON_ERROR_UTF16 (integer): Single unpaired UTF-16 surrogate in unicode escape contained in the JSON string passed to json_encode(). Available since PHP 7.0.0.

下面的常量可以和 json_decode() 的 form 选项结合使用。

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_OBJECT_AS_ARRAY (integer): Decodes JSON objects as PHP array. This option can be added automatically by calling json_decode() with the second parameter equal to TRUE. Available since PHP 5.4.0.

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_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。
JSON_PARTIAL_OUTPUT_ON_ERROR (integer): Substitute some unencodable values instead of failing. Available since PHP 5.5.0.
JSON_PRESERVE_ZERO_FRACTION (integer): Ensures that float values are always encoded as a float value. Available since PHP 5.6.6.
JSON_UNESCAPED_LINE_TERMINATORS (integer): The line terminators are kept unescaped when JSON_UNESCAPED_UNICODE is supplied. It uses the same behaviour as it was before PHP 7.1 without this constant. Available since PHP 7.1.0.

User Contributed Notes

Anonymous 28-Sep-2018 08:52


flags JSON_NUMERIC_CHECK and JSON_PRESERVE_ZERO_FRACTION are broken in php 7+ — json_encode((float)8.8) returns "8.8000000000000007", and json_encode((float)8.8, JSON_NUMERIC_CHECK) and json_encode((float)8.8, JSON_PRESERVE_ZERO_FRACTION) return "8.8000000000000007" too.



the only way to fix this is setting "serialize_precision = -1" in php.ini

ASchmidt at Anamera dot net 20-May-2018 03:53


In a multi-level array, JSON_FORCE_OBJECT will encode ALL nested numeric arrays as objects. 



If your concern was ONLY the first-level array (e.g., to make it suitable as a MySQL JSON column), you could just cast your first-level array to object, e.g.:



<?php

$json = json_encode( (object) $array, JSON_PRESERVE_ZERO_FRACTION+JSON_UNESCAPED_UNICODE );

?>



Or, if you have large arrays and are concerned about the overhead of object casting, you could append a "null" value beyond the size of the array, which will force the array to become associative:



<?php

$beyond = count( $array ) + 1;

if ( !array_key_exists( $beyond, $array) )

     $array[ $beyond ] = NULL;

$json = json_encode( $array, JSON_PRESERVE_ZERO_FRACTION+JSON_UNESCAPED_UNICODE );

?>



Of course, your later code has to treat an element with a "NULL" value the same as "!isset()", if it iterates the array.

majid4466 at gmail dot com 07-Jul-2016 05:57


To get a really clean json string use these three constants like so:



<?php

$array = ['€', 'http://example.com/some/cool/page', '337'];

$bad   = json_encode($array); 

$good  = json_encode($array,  JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES | JSON_NUMERIC_CHECK);



// $bad would be  ["\u20ac","http:\/\/example.com\/some\/cool\/page","337"]

// $good would be ["€","http://example.com/some/cool/page",337]

?>

JuanP 24-Nov-2015 01:42


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

Anonymous 13-Jun-2015 07:58


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":"????"}

on5wis at mac dot com 24-Apr-2015 09:27


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

Yzmir Ramirez 23-Sep-2014 12:31


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