(PHP 5 >= 5.2.0, PHP 7, PHP 8, PECL json >= 1.2.0)
json_encode — Retorna la representación JSON de un valor
Retorna una cadena de caracteres que contiene la representación JSON del valor
value. Si el parámetro es un array o un object, será
serializado de manera recursiva.
Si uno de los valores a serializar es un objeto, entonces por defecto solo las propiedades visibles públicamente serán incluidas. Una clase puede implementar JsonSerializable para controlar cómo sus valores son serializados en JSON.
La codificación es afectada por los flags proporcionados.
Además, la codificación de valores flotantes depende del valor de
serialize_precision.
valueEl valor a codificar. Puede ser de cualquier tipo, excepto un recurso.
Todas las cadenas deben estar codificadas en UTF-8.
Nota:
PHP implementa un superconjunto de JSON tal como se especifica en la » RFC 7159 original.
flags
Máscara de bits 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 las constantes JSON.
depthDefine la profundidad máxima. Debe ser superior a cero.
| Versión | Descripción |
|---|---|
| 7.3.0 |
El flags
JSON_THROW_ON_ERROR fue añadido.
|
| 7.2.0 |
Los flags
JSON_INVALID_UTF8_IGNORE y
JSON_INVALID_UTF8_SUBSTITUTE fueron añadidos.
|
| 7.1.0 |
El flags
JSON_UNESCAPED_LINE_TERMINATORS fue añadido.
|
| 7.1.0 | serialize_precision es utilizado en lugar de precision al codificar valores float. |
Ejemplo #1 Ejemplo con 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 Ejemplo con json_encode() mostrando algunos flags en acción
<?php
$a = array('<foo>',"'bar'",'"baz"','&blong&', "\xc3\xa9");
echo "Normal : ", json_encode($a), "\n";
echo "Tags : ", json_encode($a, JSON_HEX_TAG), "\n";
echo "Apos : ", json_encode($a, JSON_HEX_APOS), "\n";
echo "Quot : ", json_encode($a, JSON_HEX_QUOT), "\n";
echo "Amp : ", json_encode($a, JSON_HEX_AMP), "\n";
echo "Unicode : ", json_encode($a, JSON_UNESCAPED_UNICODE), "\n";
echo "Todas : ", json_encode($a, JSON_HEX_TAG | JSON_HEX_APOS | JSON_HEX_QUOT | JSON_HEX_AMP | JSON_UNESCAPED_UNICODE), "\n\n";
$b = array();
echo "Array vacío como array : ", json_encode($b), "\n";
echo "Array vacío como objeto : ", json_encode($b, JSON_FORCE_OBJECT), "\n\n";
$c = array(array(1,2,3));
echo "Array no asociativo como array : ", json_encode($c), "\n";
echo "Array no asociativo como objeto : ", json_encode($c, JSON_FORCE_OBJECT), "\n\n";
$d = array('foo' => 'bar', 'baz' => 'long');
echo "Array asociativo mostrado como objeto: ", json_encode($d), "\n";
echo "Array asociativo mostrado como objeto: ", json_encode($d, JSON_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"]
Todas : ["\u003Cfoo\u003E","\u0027bar\u0027","\u0022baz\u0022","\u0026blong\u0026","é"]
Array vacío como array : []
Array vacío como objeto : {}
Array no asociativo como array : [[1,2,3]]
Array no asociativo como objeto : {"0":{"0":1,"1":2,"2":3}}
Array asociativo mostrado como objeto: {"foo":"bar","baz":"long"}
Array asociativo mostrado como objeto: {"foo":"bar","baz":"long"}
Ejemplo #3 Ejemplo con la opción JSON_NUMERIC_CHECK
<?php
echo "Las cadenas que representan números son convertidas automáticamente a números".PHP_EOL;
$numbers = array('+123123', '-123123', '1.2e3', '0.00001');
var_dump(
$numbers,
json_encode($numbers, JSON_NUMERIC_CHECK)
);
echo "Cadenas que contienen números no formateados correctamente".PHP_EOL;
$strings = array('+a33123456789', 'a123');
var_dump(
$strings,
json_encode($strings, JSON_NUMERIC_CHECK)
);
?>El resultado del ejemplo sería algo similar a:
Las cadenas que representan números son convertidas automáticamente a 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]"
Cadenas que contienen números no formateados correctamente
array(2) {
[0]=>
string(13) "+a33123456789"
[1]=>
string(4) "a123"
}
string(24) "["+a33123456789","a123"]"
Ejemplo #4 Ejemplo con un array secuencial y un array no secuencial
<?php
echo "Array secuencial".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 eliminada".PHP_EOL;
unset($sequential[1]);
var_dump(
$sequential,
json_encode($sequential)
);
?>El resultado del ejemplo sería:
Array secuencial
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 eliminada
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 con la opción JSON_PRESERVE_ZERO_FRACTION
<?php
var_dump(json_encode(12.0, JSON_PRESERVE_ZERO_FRACTION));
var_dump(json_encode(12.0));
?>El resultado del ejemplo sería:
string(4) "12.0" string(2) "12"
Nota:
Cuando ocurre un error durante la codificación, la función json_last_error() puede ser utilizada para determinar la naturaleza exacta del error.
Nota:
Al codificar un array, si las claves no están en forma de una secuencia numérica continua comenzando en 0, todas las claves serán codificadas como cadenas de caracteres, y especificadas explícitamente para cada par clave-valor.
Nota:
Al igual que el codificador JSON de referencia, la función json_encode() generará un JSON que es un valor simple (ni un objeto, ni un array) si una string, un int, un float, o un bool es proporcionado como entrada para el parámetro
value. Aunque algunos decodificadores aceptan estos valores como JSON válido, otros no los aceptan, sabiendo que la especificación es ambigua sobre este punto.Para resumir, siempre se debe probar que su decodificador JSON puede manejar la salida que se genera desde la función json_encode().
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!Beware of Trailing Backslashes!
The JSON specification *does not allow* trailing backslashes in strings. It will create a JSON-encoded string without throwing an error, but this string will cause an error when parsed.
For example, the string "Example\" will cause the following error in JavaScript when parsing:
JSON.parse: expected ',' or '}' after property value in object
This appears to be an oversight in the JSON specification and the only work-around appears to be removing trailing slashes from all strings before encoding.Notice that JSON_FORCE_OBJECT will convert all non-associative arrays to objects. This is not necessarily a good solution for empty arrays.
If you want to convert only empty arrays to objects, simply convert them to empty object before use json_encode function.
For example:
<?php
$foo=array(
'empty2object'=>(object)[],
'empty2array'=>[],
);
echo json_encode($foo); // {"empty2object":{},"empty2array":[]}
?>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);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.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));
?>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.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;
?>The Problem:
---------------
When you filter an array in PHP using array_filter, the original keys are preserved. If you remove elements, you'll end up with gaps in the keys (non-consecutive). When encoded to JSON, this can lead to the list being interpreted as a JSON object instead of a JSON array, which might not be what your JavaScript code expects.
The Solution:
---------------
The array_values() function is essential in this scenario. It re-indexes the array with consecutive numerical keys (0, 1, 2, ...), ensuring that the JSON output is always a well-formed array.
Example:
----------
<?php
// Use Case: Filtering a list and ensuring consistent JSON array output
// Imagine you have a list of items and need to send a filtered version to a JavaScript frontend
// using JSON. You want to ensure the filtered list is always received as a JSON array,
// regardless of which items were removed.
// Sample data: A list of items
$items = [
"first",
"second",
"third",
"fourth",
"fifth"
];
// Items to remove from the list
$itemsToRemove = ["second", "fourth"];
// Filter the list, keeping original keys (which become non-consecutive)
$filteredItems = array_filter($items, function($item) use ($itemsToRemove) {
return !in_array($item, $itemsToRemove);
});
// Prepare data for JSON output
$output_arr = [
"list" => $filteredItems
];
// Output 1: JSON with non-consecutive keys (becomes an object)
echo "Output without array_values:\n";
echo json_encode($output_arr, JSON_PRETTY_PRINT) . "\n\n";
/* Output:
{
"list": {
"0": "first",
"2": "third",
"4": "fifth"
}
}
*/
// Reset keys to be consecutive using array_values
$output_arr['list'] = array_values($output_arr['list']);
// Output 2: JSON with consecutive keys (remains an array)
echo "Output with array_values:\n";
echo json_encode($output_arr, JSON_PRETTY_PRINT) . "\n";
/* Output:
{
"list": [
"first",
"third",
"fifth"
]
}
*/
?>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);
?>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);