json_encode

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

json_encodeRetorna la representación JSON del valor dado

Descripción

json_encode(mixed $value, int $flags = 0, int $depth = 512): string|false

Devuelve un string con la representación JSON de value.

La codificación se ve afectada por los flags suministrados y además la codificación de los valores de tipo float dependen del valor de serialize_precision.

Parámetros

value

El value a ser codificado. Puede ser de cualquier tipo menos un resource.

Todos los datos de tipo string deben estar codificados con UTF-8.

Nota:

PHP implementa un superconjunto de JSON tal como se especifica en la » RFC 7159 original.

flags

Máscara de bits que compuesta por JSON_FORCE_OBJECT, JSON_HEX_QUOT, JSON_HEX_TAG, JSON_HEX_AMP, JSON_HEX_APOS, JSON_INVALID_UTF8_IGNORE, JSON_INVALID_UTF8_SUBSTITUTE, JSON_NUMERIC_CHECK, JSON_PARTIAL_OUTPUT_ON_ERROR, JSON_PRESERVE_ZERO_FRACTION, JSON_PRETTY_PRINT, JSON_UNESCAPED_LINE_TERMINATORS, JSON_UNESCAPED_SLASHES, JSON_UNESCAPED_UNICODE, JSON_THROW_ON_ERROR. El comportamiento de estas constantes se describe en la página de constantes de JSON.

depth

Establece la profundidad máxima. Debe ser mayor que cero.

Valores devueltos

Devuelve un string JSON codificado en caso de éxito o false en caso de error.

Historial de cambios

Versión Descripción
7.3.0 JSON_THROW_ON_ERROR Se añadió a flags.
7.2.0 JSON_INVALID_UTF8_IGNORE, and JSON_INVALID_UTF8_SUBSTITUTE Se añadieron a flags.
7.1.0 JSON_UNESCAPED_LINE_TERMINATORS Se añadió a flags.
7.1.0 serialize_precision se utiliza en lugar de precision al codificar 'doubles'.

Ejemplos

Ejemplo #1 Un ejemplo de json_encode()

<?php
$arr 
= array('a' => 1'b' => 2'c' => 3'd' => 4'e' => 5);

echo 
json_encode($arr);
?>

El resultado del ejemplo sería:

{"a":1,"b":2,"c":3,"d":4,"e":5}

Ejemplo #2 Un ejemplo de json_encode() mostrando algunas de las opciones en acción

<?php
$a 
= array('<foo>',"'bar'",'"baz"','&blong&'"\xc3\xa9");

echo 
"Normal: ",  json_encode($a), "\n";
echo 
"Tags: ",    json_encode($aJSON_HEX_TAG), "\n";
echo 
"Apos: ",    json_encode($aJSON_HEX_APOS), "\n";
echo 
"Quot: ",    json_encode($aJSON_HEX_QUOT), "\n";
echo 
"Amp: ",     json_encode($aJSON_HEX_AMP), "\n";
echo 
"Unicode: "json_encode($aJSON_UNESCAPED_UNICODE), "\n";
echo 
"All: ",     json_encode($aJSON_HEX_TAG JSON_HEX_APOS JSON_HEX_QUOT JSON_HEX_AMP JSON_UNESCAPED_UNICODE), "\n\n";

$b = array();

echo 
"Array vacío retornado como array: "json_encode($b), "\n";
echo 
"Array vacío retornado como object: "json_encode($bJSON_FORCE_OBJECT), "\n\n";

$c = array(array(1,2,3));

echo 
"Array no asociativo retornado como array: "json_encode($c), "\n";
echo 
"Array no asociativo retornado como objeto: "json_encode($cJSON_FORCE_OBJECT), "\n\n";

$d = array('foo' => 'bar''baz' => 'long');

echo 
"Array asociativo siempre es retornado como objeto: "json_encode($d), "\n";
echo 
"Array asociativo siempre es retornado como objeto: "json_encode($dJSON_FORCE_OBJECT), "\n\n";

?>

El resultado del ejemplo sería:

Normal: ["<foo>","'bar'","\"baz\"","&blong&","\u00e9"]
Tags: ["\u003Cfoo\u003E","'bar'","\"baz\"","&blong&","\u00e9"]
Apos: ["<foo>","\u0027bar\u0027","\"baz\"","&blong&","\u00e9"]
Quot: ["<foo>","'bar'","\u0022baz\u0022","&blong&","\u00e9"]
Amp: ["<foo>","'bar'","\"baz\"","\u0026blong\u0026","\u00e9"]
Unicode: ["<foo>","'bar'","\"baz\"","&blong&","é"]
All: ["\u003Cfoo\u003E","\u0027bar\u0027","\u0022baz\u0022","\u0026blong\u0026","é"]

Array vacío retornado como array: []
Array vacío retornado como object: {}

Array no asociativo retornado como array: [[1,2,3]]
Array no asociativo retornado como objeto: {"0":{"0":1,"1":2,"2":3}}

Array asociativo siempre es retornado como objeto: {"foo":"bar","baz":"long"}
Array asociativo siempre es retornado como objeto: {"foo":"bar","baz":"long"}

Ejemplo #3 Ejemplo de la opción JSON_NUMERIC_CHECK

<?php
echo "Los string que representan números automáticamente se convierten en números".PHP_EOL;
$numbers = array('+123123''-123123''1.2e3''0.00001');
var_dump(
 
$numbers,
 
json_encode($numbersJSON_NUMERIC_CHECK)
);
echo 
"String que contienen números formateados incorrectamente".PHP_EOL;
$strings = array('+a33123456789''a123');
var_dump(
 
$strings,
 
json_encode($stringsJSON_NUMERIC_CHECK)
);
?>

El resultado del ejemplo sería:

Los string que representan números automáticamente se convierten en números
array(4) {
  [0]=>
  string(7) "+123123"
  [1]=>
  string(7) "-123123"
  [2]=>
  string(5) "1.2e3"
  [3]=>
  string(7) "0.00001"
}
string(28) "[123123,-123123,1200,1.0e-5]"
String que contienen números formateados incorrectamente
array(2) {
  [0]=>
  string(13) "+a33123456789"
  [1]=>
  string(4) "a123"
}
string(24) "["+a33123456789","a123"]"

Ejemplo #4 Ejemplo de array secuencial contra array no secuencial

<?php
echo "Array sencuencial".PHP_EOL;
$sequential = array("foo""bar""baz""blong");
var_dump(
 
$sequential,
 
json_encode($sequential)
);

echo 
PHP_EOL."Array no secuencial".PHP_EOL;
$nonsequential = array(1=>"foo"2=>"bar"3=>"baz"4=>"blong");
var_dump(
 
$nonsequential,
 
json_encode($nonsequential)
);

echo 
PHP_EOL."Array secuencial con una clave destruida".PHP_EOL;
unset(
$sequential[1]);
var_dump(
 
$sequential,
 
json_encode($sequential)
);
?>

El resultado del ejemplo sería:

Array sencuencial
array(4) {
  [0]=>
  string(3) "foo"
  [1]=>
  string(3) "bar"
  [2]=>
  string(3) "baz"
  [3]=>
  string(5) "blong"
}
string(27) "["foo","bar","baz","blong"]"

Array no secuencial"
array(4) {
  [1]=>
  string(3) "foo"
  [2]=>
  string(3) "bar"
  [3]=>
  string(3) "baz"
  [4]=>
  string(5) "blong"
}
string(43) "{"1":"foo","2":"bar","3":"baz","4":"blong"}"

Array secuencial con una clave destruida
array(3) {
  [0]=>
  string(3) "foo"
  [2]=>
  string(3) "baz"
  [3]=>
  string(5) "blong"
}
string(33) "{"0":"foo","2":"baz","3":"blong"}"

Ejemplo #5 Ejemplo de la opción JSON_PRESERVE_ZERO_FRACTION

<?php
var_dump
(json_encode(12.0JSON_PRESERVE_ZERO_FRACTION));
var_dump(json_encode(12.0));
?>

El resultado del ejemplo sería:

string(4) "12.0"
string(2) "12"

Notas

Nota:

En el evento de un fallo a codificar, json_last_error() puede ser usado para determinar la naturaleza exacta del error.

Nota:

Cuando se codifica un array, si las claves no están en una secuencia numérica continua comenzando por 0, todas las claves son codificadas como cadenas, y explícitamente especificadas para cada pareja clave-valor.

Nota:

Al igual que el codificador JSON de referencia, json_encode() generará JSON que es un valor simple (esto es, ni un objeto ni un array) si de proporciona un string, integer, float o boolean como entrada de value. Mientras que muchos decodificadores aceptarán estos valores como JSON válido, algunos no lo harán, ya que la especificación es ambigua en este aspecto.

Para resumir, compruebe siempre que el decodificador de JSON puede manejar la salida que se genere desde json_encode().

Ver también

add a note

User Contributed Notes 14 notes

up
103
bohwaz
10 years ago
Are you sure you want to use JSON_NUMERIC_CHECK, really really sure?

Just watch this usecase:

<?php
// International phone number
json_encode(array('phone_number' => '+33123456789'), JSON_NUMERIC_CHECK);
?>

And then you get this JSON:

{"phone_number":33123456789}

Maybe it makes sense for PHP (as is_numeric('+33123456789') returns true), but really, casting it as an int?!

So be careful when using JSON_NUMERIC_CHECK, it may mess up with your data!
up
1
DimeCadmium
7 months ago
> While most decoders will accept these values as valid JSON, some may not, as the specification is ambiguous on this point.

The specification (https://datatracker.ietf.org/doc/html/rfc8259#section-2) is not ambiguous, whether you look at RFC8259, go back to RFC7159 or 7158 or 4627, look at (either edition of) ECMA-404, or even at JSON.org.

The original RFC - from 16 years ago, mind you - specified that the root level of JSON text could only be a object or array.

Literally every other standard - from as long as 9 years ago (RFC7158 and ECMA-404 1st Ed.) and as recent as 5 years ago (RFC8259 and ECMA-404 2nd Ed., both current standards) - makes explicit that any value can appear at the root.
up
9
ryan at ryanparman dot com
12 years ago
I came across the "bug" where running json_encode() over a SimpleXML object was ignoring the CDATA. I ran across http://bugs.php.net/42001 and http://bugs.php.net/41976, and while I agree with the poster that the documentation should clarify gotchas like this, I was able to figure out how to workaround it.

You need to convert the SimpleXML object back into an XML string, then re-import it back into SimpleXML using the LIBXML_NOCDATA option. Once you do this, then you can use json_encode() and still get back the CDATA.

<?php
// Pretend we already have a complex SimpleXML object stored in $xml
$json = json_encode(new SimpleXMLElement($xml->asXML(), LIBXML_NOCDATA));
?>
up
3
Nick
6 years ago
Please note that there was an (as of yet) undocumented change to the json_encode() function between 2 versions of PHP with respect to JSON_PRETTY_PRINT:

In version 5.4.21 and earlier, an empty array [] using JSON_PRETTY_PRINT would be rendered as 3 lines, with the 2nd one an empty (indented) line, i.e.:
    "data": [
       
    ],

In version 5.4.34 and above, an empty array [] using JSON_PRETTY_PRINT would be rendered as exactly [] at the spot where it occurs, i.e.
    "data: [],

This is not mentioned anywhere in the PHP changelist and migration documentations; neither on the json_encode documentation page.

This is very useful to know when you are parsing the JSON using regular expressions to manually insert portions of data, as is the case with my current use-case (working with JSON exports of over several gigabytes requires sub-operations and insertion of data).
up
9
guilhenfsu at gmail dot com
9 years ago
Solution for UTF-8 Special Chars.

<?

$array = array('nome'=>'Paição','cidade'=>'São Paulo');

$array = array_map('htmlentities',$array);

//encode
$json = html_entity_decode(json_encode($array));

//Output: {"nome":"Paição","cidade":"São Paulo"}
echo $json;

?>
up
1
ck at ergovia dot de
9 years ago
Attention when passing a plain array to json_encode and using JSON_FORCE_OBJECT. It figured out that the index-order of the resulting JSON-string depends on the system PHP is running on.

$a = array("a" , "b", "c");
echo json_encode($a, JSON_FORCE_OBJECT);

On Xampp (Windows) you get:

{"0":"a","1":"b","2":"c"}';

On a machine running debian I get:

{"2":"a","1":"b","0":"c"}';

Note that the key:value pairs are different!

Solution here was to use array_combine to create a ssociative array and then pass it to json_encode:

json_encode(array_combine(range(0, count($a) - 1), $a), JSON_FORCE_OBJECT);
up
3
Walter Tross
6 years ago
If you need pretty-printed output, but want it indented by 2 spaces instead of 4:

$json_indented_by_4 = json_encode($output, JSON_UNESCAPED_SLASHES|JSON_PRETTY_PRINT);
$json_indented_by_2 = preg_replace('/^(  +?)\\1(?=[^ ])/m', '$1', $json_indented_by_4);
up
3
Istratov Vadim
13 years ago
Be careful with floating values in some locales (e.g. russian) with comma (",") as decimal point. Code:

<?php
setlocale
(LC_ALL, 'ru_RU.utf8');

$arr = array('element' => 12.34);
echo
json_encode( $arr );
?>

Output will be:
--------------
{"element":12,34}
--------------

Which is NOT a valid JSON markup. You should convert floating point variable to strings or set locale to something like "LC_NUMERIC, 'en_US.utf8'" before using json_encode.
up
0
jakepucan at gmail dot com
1 year ago
It's also  worth mentioning that adding charset is fine.

<?php
header
('Content-type:application/json;charset=utf-8');
json_encode(['name' => 'Jake', 'country' => 'Philippines']);
up
2
Sam Barnum
13 years ago
Note that if you try to encode an array containing non-utf values, you'll get null values in the resulting JSON string.  You can batch-encode all the elements of an array with the array_map function:
<?php
$encodedArray
= array_map(utf8_encode, $rawArray);
?>
up
1
spam.goes.in.here AT gmail.com
14 years ago
For anyone who has run into the problem of private properties not being added, you can simply implement the IteratorAggregate interface with the getIterator() method. Add the properties you want to be included in the output into an array in the getIterator() method and return it.
up
1
Garrett
13 years ago
A note about json_encode automatically quoting numbers:

It appears that the json_encode function pays attention to the data type of the value. Let me explain what we came across:

We have found that when retrieving data from our database, there are occasions when numbers appear as strings to json_encode which results in double quotes around the values.

This can lead to problems within javascript functions expecting the values to be numeric.

This was discovered when were were retrieving fields from the database which contained serialized arrays. After unserializing them and sending them through the json_encode function the numeric values in the original array were now being treated as strings and showing up with double quotes around them.

The fix: Prior to encoding the array, send it to a function which checks for numeric types and casts accordingly. Encoding from then on worked as expected.
up
-1
pvl dot kolensikov at gmail dot com
11 years ago
As json_encode() is recursive, you can use it to serialize whole structure of objects.

<?php
class A {
    public
$a = 1;
    public
$b = 2;
    public
$collection = array();

    function 
__construct(){
        for (
$i=3; $i-->0;){
           
array_push($this->collection, new B);
        }
    }
}

class
B {
    public
$a = 1;
    public
$b = 2;
}

echo
json_encode(new A);
?>

Will give:

{
    "a":1,
    "b":2,
    "collection":[{
        "a":1,
        "b":2
    },{
        "a":1,
        "b":2
    },{
        "a":1,
        "b":2
    }]
}
up
-1
mikko dot rantalainen at peda dot net
1 year ago
Notice that <?php $json = json_encode($x, JSON_FORCE_OBJECT); ?> doesn't guarantee that $json is actually an object encoded with JSON syntax. It *only* guarantees that the output doesn't start with "[".

For example:
<?php
json_encode
("foo", JSON_FORCE_OBJECT); # "foo"
json_encode(42, JSON_FORCE_OBJECT); # 42
json_encode(false, JSON_FORCE_OBJECT); # false
json_encode("false", JSON_FORCE_OBJECT); # "false"
json_encode(10/3, JSON_FORCE_OBJECT); # 3.3333333333333335
?>
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