PHP 8.1.0 Released!

json_decode

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

json_decodeDecodes 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 variable.

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.

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 in appropriate PHP type. 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.

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($json));
var_dump(json_decode($jsontrue));

?>

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(
        
=> array(
            
'English' => array(
                
'One',
                
'January'
            
),
            
'French' => array(
                
'Une',
                
'Janvier'
            
)
        )
    )
);

// Show the errors for different depths.
var_dump(json_decode($jsontrue4));
echo 
'Last error: 'json_last_error_msg(), PHP_EOLPHP_EOL;

var_dump(json_decode($jsontrue3));
echo 
'Last error: 'json_last_error_msg(), PHP_EOLPHP_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($json));
var_dump(json_decode($jsonfalse512JSON_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

add a note add a note

User Contributed Notes 6 notes

up
5
Alien426
7 months ago
Browsers don't choke on integers _starting_ with BigInt (64 bits), but before that (53 bits). The introduction of BigInt to modern browsers doesn't help much, when JSON handling functions do not support it. So I am trying to remedy that. My approach is to handle the decoded array before re-encoding it to a string:
<?php
function fix_large_int(&$value)
{
  if (
is_int($value) && $value > 9007199254740991)
   
$value = strval($value);
}
$json_str = '{"id":[1234567890123456789,12345678901234567890]}';
$json_arr = json_decode($json_str, flags: JSON_BIGINT_AS_STRING | JSON_OBJECT_AS_ARRAY);
echo(
json_encode($json_arr)); // {"id":[1234567890123456789,"12345678901234567890"]} (BigInt is already converted to a string here)
array_walk_recursive($json_arr, 'fix_large_int');
echo(
json_encode($json_arr)); // {"id":["1234567890123456789","12345678901234567890"]}
?>
up
3
cubefox at web dot NOSPAMPLEASE dot de
1 year ago
Warning: As the section "return values" mentions, the return value NULL is ambiguos. To repeat, it can mean three things:

* The input string had the value "null"
* There was an error while parsing the input data
* The encoded data was deeper than the recursion limit

To distinguish these cases, json_last_error() can be used.
up
1
as-works at narod dot ru
21 days ago
On some PHP7+ systems php_json functions can be undefined (i faced it on Oracle Linux Enterprice with php 7.4 installed from REMI repository). If you have the same problem, try to install separated php-json module:

# yum install php-json

Hope this helps.
up
-3
Anonymous
2 months ago
<?php

$array
= [0 => "foo", 1 => "bar", 2 => ["baz"]];

$associative = false;

var_dump(
   
json_decode(
       
json_encode($array),
       
$associative
   
)
);

?>

The above will output
<?php
/*
array (size=3)
  0 => string 'foo' (length=3)
  1 => string 'bar' (length=3)
  2 =>
    array (size=1)
      0 => string 'baz' (length=3)
*/
?>

Considering <?php $associative = false; ?> one might expect
<?php
/*
object(stdClass)
  public '0' => string 'foo' (length=3)
  public '1' => string 'bar' (length=3)
  public '2' =>
    object(stdClass)
      public '0' => string 'baz' (length=3)
*/
?>

an stdClass object instead of an array, but this is incorrect.
json_decode will always return an array for a sequentially encoded array, regardless of the ?bool $associative 2nd argument

Which is inline with the above mentioned docs/spec
    > Returns the value encoded in json in appropriate PHP type

Considering that the 1st arg was a sequentially encoded array as a json string
    '["foo","bar",["baz"]]'
up
-4
greaties at ghvernuft dot nl
7 months ago
To load an object with data in json format:

function loadJSON($Obj, $json)
{
    $dcod = json_decode($json);
    $prop = get_object_vars ( $dcod );
    foreach($prop as $key => $lock)
    {
        if(property_exists ( $Obj ,  $key ))
        {
            if(is_object($dcod->$key))
            {
                loadJSON($Obj->$key, json_encode($dcod->$key));
            }
            else
            {
                $Obj->$key = $dcod->$key;
            }
        }
    }
}
up
-21
mattia
9 months ago
if you're using ajax to post, and your JavaScript code looks like this:

<code>
    var xhttp = new XMLHttpRequest();
    xhttp.open("POST", "something.php", true);
    xhttp.setRequestHeader("Content-Type", "application/json");
    xhttp.onreadystatechange = function() {
        if (this.readyState == 4 && this.status == 200) {
             // do something
        }
    };
    var data = {some: "thing"};
    xhttp.send(JSON.stringify(data));
</code>

then in <code>something.php</code> you can retrieve your json by doing

<?php
$data
= json_decode(file_get_contents("php://input"), true);
?>
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