Standard distributions of PHP have the JSON support enabled by default. The PHP extension implements the JavaScript Object Notation (JSON) data interchange format. The JSON extension in PHP parser handles the JSON data.
JSON (JavaScript Object Notation) is a lightweight, text-based, language-independent data interchange format. JSON defines a small set of formatting rules for the portable representation of structured data. It is a text based data format that is easy for the humans as well as machines to read.
The JSON extension in PHP version 5.2 onwards provides a number of predefined constants, JSON related functions, and also a JsonException class.
PHP JSON Functions
PHP has the following JSON functions −
json_encode()
This function returns a string containing the JSON representation of the supplied value. If the parameter is an array or object, it will be serialized recursively.
json_encode(mixed $value, int $flags = 0, int $depth = 512): string|false
json_decode()
This function takes a JSON encoded string and converts it into a PHP value.
json_decode( string $json, ?bool $associative = null, int $depth = 512, int $flags = 0 ): mixed
When the associative parameter of this function is true, JSON objects will be returned as associative arrays; when false, JSON objects will be returned as objects.
The encode/decode operations are affected by the supplied flags. The predefined constants and their integer values are as below −
| Predefined Constant | Values |
|---|---|
| JSON_HEX_TAG | 1 |
| JSON_HEX_AMP | 2 |
| JSON_HEX_APOS | 4 |
| JSON_HEX_QUOT | 8 |
| JSON_FORCE_OBJECT | 16 |
| JSON_NUMERIC_CHECK | 32 |
| JSON_UNESCAPED_SLASHES | 64 |
| JSON_PRETTY_PRINT | 128 |
| JSON_UNESCAPED_UNICODE | 256 |
json_last_error_msg()
This function returns the error string of the last json_encode() or json_decode() call.
json_last_error_msg(): string
“No error” message is returned if no error has occurred.
json_last_error()
This function returns an integer.
json_last_error(): int
The function returns an integer corresponding to one of the following constants −
| Sr.No | Constant & Meaning |
|---|---|
| 1 |
JSON_ERROR_NONE No error has occurred |
| 2 |
JSON_ERROR_DEPTH The maximum stack depth has been exceeded |
| 3 |
JSON_ERROR_STATE_MISMATCH Invalid or malformed JSON |
| 4 |
JSON_ERROR_CTRL_CHAR Control character error, possibly incorrectly encoded |
| 5 |
JSON_ERROR_SYNTAX Syntax error |
| 6 |
JSON_ERROR_UTF8 Malformed UTF-8 characters, possibly incorrectly encoded |
| 7 |
JSON_ERROR_RECURSION One or more recursive references in the value to be encoded |
| 8 |
JSON_ERROR_INF_OR_NAN One or more NAN or INF values in the value to be encoded |
| 9 | JSON_ERROR_UNSUPPORTED_TYPE
A value of a type that cannot be encoded was given |
| 10 |
JSON_ERROR_INVALID_PROPERTY_NAME A property name that cannot be encoded was given |
| 11 |
JSON_ERROR_UTF16 Malformed UTF-16 characters, possibly incorrectly encoded |
Example
The following PHP code encodes a given array to JSON representation, and decodes the JSON string back to PHP array.
<?php
$arr = array(''a'' => 1, ''b'' => 2, ''c'' => 3, ''d'' => 4, ''e'' => 5);
$encoded = json_encode($arr);
echo "The initial array: " . PHP_EOL;
var_dump($arr);
echo "Encoded JSON: $encoded" . PHP_EOL;
$decoded = json_decode($encoded);
echo "Array obtained after decoding: " . PHP_EOL;
var_dump($decoded);
?>
It will produce the following output −
The initial array:
array(5) {
["a"]=>
int(1)
["b"]=>
int(2)
["c"]=>
int(3)
["d"]=>
int(4)
["e"]=>
int(5)
}
Encoded JSON: {"a":1,"b":2,"c":3,"d":4,"e":5}
Array obtained after decoding:
object(stdClass)#1 (5) {
["a"]=>
int(1)
["b"]=>
int(2)
["c"]=>
int(3)
["d"]=>
int(4)
["e"]=>
int(5)
}