Predefined Constants

The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.

The following constants indicate the type of error returned by json_last_error() or stored as the code of a JsonException.

JSON_ERROR_NONE (int): No error has occurred.
JSON_ERROR_DEPTH (int): The maximum stack depth has been exceeded.
JSON_ERROR_STATE_MISMATCH (int): Occurs with underflow or with the modes mismatch.
JSON_ERROR_CTRL_CHAR (int): Control character error, possibly incorrectly encoded.
JSON_ERROR_SYNTAX (int): Syntax error.
JSON_ERROR_UTF8 (int): Malformed UTF-8 characters, possibly incorrectly encoded.
JSON_ERROR_RECURSION (int): 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.
JSON_ERROR_INF_OR_NAN (int): 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.
JSON_ERROR_UNSUPPORTED_TYPE (int): 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.
JSON_ERROR_INVALID_PROPERTY_NAME (int): A key starting with \u0000 character was in the string passed to json_decode() when decoding a JSON object into a PHP object.
JSON_ERROR_UTF16 (int): Single unpaired UTF-16 surrogate in unicode escape contained in the JSON string passed to json_decode().

The following constants can be combined to form options for json_decode().

JSON_BIGINT_AS_STRING (int): Decodes large integers as their original string value.
JSON_OBJECT_AS_ARRAY (int): Decodes JSON objects as PHP array. This option can be added automatically by calling json_decode() with the second parameter equal to true.

The following constants can be combined to form options for json_encode().

JSON_HEX_TAG (int): All < and > are converted to \u003C and \u003E.
JSON_HEX_AMP (int): All & are converted to \u0026.
JSON_HEX_APOS (int): All ' are converted to \u0027.
JSON_HEX_QUOT (int): All " are converted to \u0022.
JSON_FORCE_OBJECT (int): Outputs an object rather than an array when a non-associative array is used. Especially useful when the recipient of the output is expecting an object and the array is empty.
JSON_NUMERIC_CHECK (int): Encodes numeric strings as numbers.
JSON_PRETTY_PRINT (int): Use whitespace in returned data to format it.
JSON_UNESCAPED_SLASHES (int): Don't escape /.
JSON_UNESCAPED_UNICODE (int): Encode multibyte Unicode characters literally (default is to escape as \uXXXX).
JSON_PARTIAL_OUTPUT_ON_ERROR (int): Substitute some unencodable values instead of failing.
JSON_PRESERVE_ZERO_FRACTION (int): Ensures that float values are always encoded as a float value.
JSON_UNESCAPED_LINE_TERMINATORS (int): 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 as of PHP 7.1.0.

The following constants can be combined to form options for json_decode() and json_encode().

JSON_INVALID_UTF8_IGNORE (int): Ignore invalid UTF-8 characters. Available as of PHP 7.2.0.
JSON_INVALID_UTF8_SUBSTITUTE (int): Convert invalid UTF-8 characters to \0xfffd (Unicode Character 'REPLACEMENT CHARACTER') Available as of PHP 7.2.0.
JSON_THROW_ON_ERROR (int): Throws JsonException if an error occurs instead of setting the global error state that is retrieved with json_last_error() and json_last_error_msg(). JSON_PARTIAL_OUTPUT_ON_ERROR takes precedence over JSON_THROW_ON_ERROR. Available as of PHP 7.3.0.
JSON_ERROR_NON_BACKED_ENUM (int): The value passed to json_encode() includes a non-backed enum which cannot be serialized. Available as of PHP 8.1.0.

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User Contributed Notes 5 notes

down

majid4466 at gmail dot com ¶

8 years ago

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]
?>

down

Yzmir Ramirez ¶

9 years ago

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

down

nikospapoutsis ¶

2 years ago

Be EXTREMELY cautious when using the code majid4466 at gmail dot com provided, or JSON_NUMERIC_CHECK in general.

For example, in php 7.4 and 8.1 with precision: 14 and serialize_precision: -1 we get:

<?php
$array = ['€', 55.6666666666666666, 'http://example.com/some/cool/page', '000337', '55.6666666666666666'];
echo $case1 = json_encode($array);
echo $case2 = json_encode($array,  JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES );
echo $case3 = json_encode($array,  JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES | JSON_NUMERIC_CHECK);

["\u20ac",55.666666666666664,"http:\/\/example.com\/some\/cool\/page","000337","55.6666666666666666"]
// in $case1, both euro sign and the url change but we also lost a digit in our unquoted float (due to precision)

["€",55.666666666666664,"http://example.com/some/cool/page","000337","55.6666666666666666"]
// in $case2, both euro sign and the url stay exactly the same but we still lost a digit in our unquoted float (due to precision)

["€",55.666666666666664,"http://example.com/some/cool/page",337,55.666666666666664]
// in $case3, we once again keep euro sign and the url intact but this time not only our unquoted float lost a digit
// but the same happened to our quoted float and the number/string lost its leading zeros too

Also, note that in php 5.x you will probably get some different but equally wrong results as default values may be different and some functions have changed internally as well.

down

ASchmidt at Anamera dot net ¶

6 years ago

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.

down

-3

Anonymous ¶

5 years ago

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

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