Decodes a JSON string

# json_decode

(PHP 5 >= 5.2.0, PHP 7, PHP 8, PECL json >= 1.2.0)

json_decode — Decodes a JSON string

### Description

json_decode(
string `$json`,
?bool `$associative` = `null`,
int `$depth` = 512,
int `$flags` = 0
): mixed

Takes a JSON encoded string and converts it into a PHP value.

### Parameters

`json`

  The `json` string being decoded.

  This function only works with UTF-8 encoded strings.

  > Note:

  > PHP implements a superset of JSON as specified in the original » RFC 7159.

`associative`

  When `true`, JSON objects will be returned as associative arrays; when `false`, JSON objects will be returned as objects. When `null`, JSON objects will be returned as associative arrays or objects depending on whether `JSON_OBJECT_AS_ARRAY` is set in the `flags`.

`depth`

  Maximum nesting depth of the structure being decoded. The value must be greater than `0`, and less than or equal to `2147483647`.

`flags`

  Bitmask of `JSON_BIGINT_AS_STRING`, `JSON_INVALID_UTF8_IGNORE`, `JSON_INVALID_UTF8_SUBSTITUTE`, `JSON_OBJECT_AS_ARRAY`, `JSON_THROW_ON_ERROR`. The behaviour of these constants is described on the JSON constants page.

### Return Values

Returns the value encoded in `json` as an appropriate PHP type. Unquoted values `true`, `false` and `null` are returned as `true`, `false` and `null` respectively. `null` is returned if the `json` cannot be decoded or if the encoded data is deeper than the nesting limit.

### Errors/Exceptions

If `depth` is outside the allowed range, a ValueError is thrown as of PHP 8.0.0, while previously, an error of level `E_WARNING` was raised.

### Changelog

Version | Description
--- | ---
7.3.0 | `JSON_THROW_ON_ERROR` `flags` was added.
7.2.0 | `associative` is nullable now.
7.2.0 | `JSON_INVALID_UTF8_IGNORE`, and `JSON_INVALID_UTF8_SUBSTITUTE` `flags` were added.
7.1.0 | An empty JSON key ("") can be encoded to the empty object property instead of using a key with value `_empty_`.

### Examples

Example #1 json_decode() examples

`<?php
$json = '{"a":1,"b":2,"c":3,"d":4,"e":5}';
var_dump(json_decode($json));
var_dump(json_decode($json, true));
?>`

The above example will output:

    object(stdClass)#1 (5) {
        ["a"] => int(1)
        ["b"] => int(2)
        ["c"] => int(3)
        ["d"] => int(4)
        ["e"] => int(5)
    }

    array(5) {
        ["a"] => int(1)
        ["b"] => int(2)
        ["c"] => int(3)
        ["d"] => int(4)
        ["e"] => int(5)
    }

Example #2 Accessing invalid object properties

Accessing elements within an object that contain characters not permitted under PHP's naming convention (e.g. the hyphen) can be accomplished by encapsulating the element name within braces and the apostrophe.

`<?php
$json = '{"foo-bar": 12345}';
$obj = json_decode($json);
print $obj->{'foo-bar'}; // 12345
?>`

Example #3 common mistakes using json_decode()

`<?php
// the following strings are valid JavaScript but not valid JSON
// the name and value must be enclosed in double quotes
// single quotes are not valid
$bad_json = "{ 'bar': 'baz' }";
json_decode($bad_json); // null
// the name must be enclosed in double quotes
$bad_json = '{ bar: "baz" }';
json_decode($bad_json); // null
// trailing commas are not allowed
$bad_json = '{ bar: "baz", }';
json_decode($bad_json); // null
?>`

Example #4 `depth` errors

`<?php
// Encode some data with a maximum depth of 4 (array -> array -> array -> string)
$json = json_encode(
array(
1 => array(
'English' => array(
'One',
'January'
),
'French' => array(
'Une',
'Janvier'
)
)
)
);
// Show the errors for different depths.
var_dump(json_decode($json, true, 4));
echo 'Last error: ', json_last_error_msg(), PHP_EOL, PHP_EOL;
var_dump(json_decode($json, true, 3));
echo 'Last error: ', json_last_error_msg(), PHP_EOL, PHP_EOL;
?>`

The above example will output:

    array(1) {
      [1]=>
      array(2) {
        ["English"]=>
        array(2) {
          [0]=>
          string(3) "One"
          [1]=>
          string(7) "January"
        }
        ["French"]=>
        array(2) {
          [0]=>
          string(3) "Une"
          [1]=>
          string(7) "Janvier"
        }
      }
    }
    Last error: No error

    NULL
    Last error: Maximum stack depth exceeded

Example #5 json_decode() of large integers

`<?php
$json = '{"number": 12345678901234567890}';
var_dump(json_decode($json));
var_dump(json_decode($json, false, 512, JSON_BIGINT_AS_STRING));
?>`

The above example will output:

    object(stdClass)#1 (1) {
      ["number"]=>
      float(1.2345678901235E+19)
    }
    object(stdClass)#1 (1) {
      ["number"]=>
      string(20) "12345678901234567890"
    }

### Notes

> Note:

> The JSON spec is not JavaScript, but a subset of JavaScript.

> Note:

> In the event of a failure to decode, json_last_error() can be used to determine the exact nature of the error.

### See Also

- json_encode() - Returns the JSON representation of a value
- json_last_error() - Returns the last error occurred
- json_last_error_msg() - Returns the error string of the last json_validate(), json_encode() or json_decode() call

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