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json_encode

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

json_encodeReturns the JSON representation of a value

Description

string json_encode ( mixed $value [, int $options = 0 [, int $depth = 512 ]] )

Returns a string containing the JSON representation of value.

Parameters

value

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 - it will also encode and decode scalar types and NULL. The JSON standard only supports these values when they are nested inside an array or an object.

options

Bitmask consisting of JSON_HEX_QUOT, JSON_HEX_TAG, JSON_HEX_AMP, JSON_HEX_APOS, JSON_NUMERIC_CHECK, JSON_PRETTY_PRINT, JSON_UNESCAPED_SLASHES, JSON_FORCE_OBJECT, JSON_UNESCAPED_UNICODE. The behaviour of these constants is described on the JSON constants page.

depth

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
5.5.0 depth parameter was added.
5.4.0 JSON_PRETTY_PRINT, JSON_UNESCAPED_SLASHES, and JSON_UNESCAPED_UNICODE options were added.
5.3.3 JSON_NUMERIC_CHECK option was added.
5.3.0 The options parameter was added.

Examples

Example #1 A json_encode() example

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

echo 
json_encode($arr);
?>

The above example will output:

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

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

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

$c = array(array(1,2,3));

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

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

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

The above example will output:

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 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)
);
?>

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) "{"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"}"

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, integer, float or boolean 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

PHP Manual