json_encode
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.
Parameters
The value being encoded. Can be any type except a resource.
All string data must be UTF-8 encoded.
Note:
PHP implements a superset of JSON as specified in the original » RFC 7159.
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.
Set the maximum depth. Must be greater than zero.
Return Values
Returns a JSON encoded string on success or false on failure.
Changelog
| Version | Description |
|---|---|
| 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. |
Examples
Example #1 A json_encode() example
$arr = array( ‘a’ => 1 , ‘b’ => 2 , ‘c’ => 3 , ‘d’ => 4 , ‘e’ => 5 );
The above example will output:
Example #2 A json_encode() example showing some flags in use
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» ;
echo «Empty array output as array: » , json_encode ( $b ), «\n» ;
echo «Empty array output as object: » , json_encode ( $b , JSON_FORCE_OBJECT ), «\n\n» ;
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» ;
?>
The above example will output:
Normal: [«»,»‘bar'»,»\»baz\»»,»&blong&»,»\u00e9″] Tags: [«\u003Cfoo\u003E»,»‘bar'»,»\»baz\»»,»&blong&»,»\u00e9″] Apos: [«»,»\u0027bar\u0027″,»\»baz\»»,»&blong&»,»\u00e9″] Quot: [«»,»‘bar'»,»\u0022baz\u0022″,»&blong&»,»\u00e9″] Amp: [«»,»‘bar'»,»\»baz\»»,»\u0026blong\u0026″,»\u00e9″] Unicode: [«»,»‘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: > Associative array always output as object: Associative array always output as object:
Example #3 JSON_NUMERIC_CHECK option example
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 )
);
?>
The above example will output something similar to:
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
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 )
);
?>
The above example will output:
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) "" Sequential array with one key unset array(3) < [0]=>string(3) "foo" [2]=> string(3) "baz" [3]=> string(5) "blong" > string(33) ""
Example #5 JSON_PRESERVE_ZERO_FRACTION option example
The above example will output:
Notes
Note:
In the event of a failure to encode, json_last_error() can be used to determine the exact nature of the error.
Note:
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.
Note:
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() .
See Also
- JsonSerializable
- json_decode() — Decodes a JSON string
- json_last_error() — Returns the last error occurred
- serialize() — Generates a storable representation of a value
User Contributed Notes 15 notes
Are you sure you want to use JSON_NUMERIC_CHECK, really really sure?
// International phone number
json_encode (array( ‘phone_number’ => ‘+33123456789’ ), JSON_NUMERIC_CHECK );
?>
And then you get this JSON:
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!
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.
$foo =array(
’empty2object’ =>(object)[],
’empty2array’ =>[],
);
echo json_encode ( $foo ); // ,»empty2array»:[]>
Be careful with floating values in some locales (e.g. russian) with comma («,») as decimal point. Code:
setlocale ( LC_ALL , ‘ru_RU.utf8’ );
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.
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 a machine running debian I get:
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);
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.
// Pretend we already have a complex SimpleXML object stored in $xml
$json = json_encode (new SimpleXMLElement ( $xml -> asXML (), LIBXML_NOCDATA ));
?>
Solution for UTF-8 Special Chars.
$array = array(‘nome’=>’Paição’,’cidade’=>’São Paulo’);
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:
$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);
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.
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).
It’s also worth mentioning that adding charset is fine.
header ( ‘Content-type:application/json;charset=utf-8’ );
json_encode ([ ‘name’ => ‘Jake’ , ‘country’ => ‘Philippines’ ]);
As json_encode() is recursive, you can use it to serialize whole structure of objects.
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:
> 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.
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.
Notice that 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:
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
?>