json_encode

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

json_encode — Returns the JSON representation of a value

Descrizione

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

Returns a string containing the JSON representation of the supplied value. If the parameter is an array or object, it will be serialized recursively.

If a value to be serialized is an object, then by default only publicly visible properties will be included. Alternatively, a class may implement JsonSerializable to control how its values are serialized to JSON.

The encoding is affected by the supplied flags and additionally the encoding of float values depends on the value of serialize_precision.

Elenco dei parametri

value

The value being encoded. Can be any type except a resource.

All string data must be UTF-8 encoded.

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

flags

Bitmask consisting of 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. The behaviour of these constants is described on the JSON constants page.

depth

Set the maximum depth. Must be greater than zero.

Valori restituiti

Returns a JSON encoded string on success o false in caso di fallimento.

Log delle modifiche

Versione	Descrizione
7.3.0	`JSON_THROW_ON_ERROR` `flags` was added.
7.2.0	`JSON_INVALID_UTF8_IGNORE`, and `JSON_INVALID_UTF8_SUBSTITUTE` `flags` were added.
7.1.0	`JSON_UNESCAPED_LINE_TERMINATORS` `flags` was added.
7.1.0	serialize_precision is used instead of precision when encoding float values.

Esempi

Example #1 A json_encode() example

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

echo json_encode($arr);
?>

Il precedente esempio visualizzerà:

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

Example #2 A json_encode() example showing some flags in use

<?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 "All: ",     json_encode($a, JSON_HEX_TAG | JSON_HEX_APOS | JSON_HEX_QUOT | JSON_HEX_AMP | JSON_UNESCAPED_UNICODE), "\n\n";

$b = array();

echo "Empty array output as array: ", json_encode($b), "\n";
echo "Empty array output as object: ", json_encode($b, JSON_FORCE_OBJECT), "\n\n";

$c = array(array(1,2,3));

echo "Non-associative array output as array: ", json_encode($c), "\n";
echo "Non-associative array output as object: ", json_encode($c, JSON_FORCE_OBJECT), "\n\n";

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

echo "Associative array always output as object: ", json_encode($d), "\n";
echo "Associative array always output as object: ", json_encode($d, JSON_FORCE_OBJECT), "\n\n";
?>

Il precedente esempio visualizzerà:

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"]

Empty array output as array: []
Empty array output as object: {}

Non-associative array output as array: [[1,2,3]]
Non-associative array output as object: {"0":{"0":1,"1":2,"2":3}}

Associative array always output as object: {"foo":"bar","baz":"long"}
Associative array always output as object: {"foo":"bar","baz":"long"}

Example #3 JSON_NUMERIC_CHECK option example

<?php
echo "Strings representing numbers automatically turned into numbers".PHP_EOL;
$numbers = array('+123123', '-123123', '1.2e3', '0.00001');
var_dump(
 $numbers,
 json_encode($numbers, JSON_NUMERIC_CHECK)
);
echo "Strings containing improperly formatted numbers".PHP_EOL;
$strings = array('+a33123456789', 'a123');
var_dump(
 $strings,
 json_encode($strings, JSON_NUMERIC_CHECK)
);
?>

Il precedente esempio visualizzerà qualcosa simile a:

Strings representing numbers automatically turned into numbers
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]"
Strings containing improperly formatted numbers
array(2) {
  [0]=>
  string(13) "+a33123456789"
  [1]=>
  string(4) "a123"
}
string(24) "["+a33123456789","a123"]"

Example #4 Sequential versus non-sequential array example

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

echo PHP_EOL."Non-sequential array".PHP_EOL;
$nonsequential = array(1=>"foo", 2=>"bar", 3=>"baz", 4=>"blong");
var_dump(
 $nonsequential,
 json_encode($nonsequential)
);

echo PHP_EOL."Sequential array with one key unset".PHP_EOL;
unset($sequential[1]);
var_dump(
 $sequential,
 json_encode($sequential)
);
?>

Il precedente esempio visualizzerà:

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

Non-sequential array
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"}"

Sequential array with one key unset
array(3) {
  [0]=>
  string(3) "foo"
  [2]=>
  string(3) "baz"
  [3]=>
  string(5) "blong"
}
string(33) "{"0":"foo","2":"baz","3":"blong"}"

Example #5 JSON_PRESERVE_ZERO_FRACTION option example

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

Il precedente esempio visualizzerà:

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

Note

Nota:
In the event of a failure to encode, json_last_error() can be used to determine the exact nature of the error.

Nota:
When encoding an array, if the keys are not a continuous numeric sequence starting from 0, all keys are encoded as strings, and specified explicitly for each key-value pair.

Nota:
Like the reference JSON encoder, json_encode() will generate JSON that is a simple value (that is, neither an object nor an array) if given a string, int, float or bool as an input value. While most decoders will accept these values as valid JSON, some may not, as the specification is ambiguous on this point.

To summarise, always test that your JSON decoder can handle the output you generate from json_encode().

Vedere anche:

JsonSerializable
json_decode() - Decodes a JSON string
json_last_error() - Returns the last error occurred
serialize() - Genera una versione archiviabile del valore

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User Contributed Notes 9 notes

down

102

bohwaz ¶

13 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!

down

elliseproduction at gmail dot com ¶

2 years ago


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":[]}

?>

down

Istratov Vadim ¶

15 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.

down

ck at ergovia dot de ¶

11 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);

down

ryan at ryanparman dot com ¶

14 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));
?>

down

guilhenfsu at gmail dot com ¶

11 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;

?>

down

Walter Tross ¶

9 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);

down

Garrett ¶

16 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.

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Sam Barnum ¶

15 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);
?>

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