# 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().
`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.

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.

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