This post covers how to use, encode and decode JSON objects when using PHP.

The functions

  • json_encode – Returns the JSON representation – link
  • json_decode – Decodes a JSON string – link
  • json_last_error_msg – Returns the error string of the last json_encode() or json_decode() call – link
  • json_last_error – Returns the last error occurred – link


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

Returns a string containing the JSON representation of the supplied $value, being the value any type except a PHP resource. For instance, an array, an object… And the value must be UTF-8 encoded. The $options parameter is a bit-mask 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_PRESERVE_ZERO_FRACTION, JSON_UNESCAPED_UNICODE, JSON_PARTIAL_OUTPUT_ON_ERROR, JSON_UNESCAPED_LINE_TERMINATORS, JSON_THROW_ON_ERROR (see predefined constants here). And finally, the $depth parameter sets the maximum depth, that must be greater than zero.


json_decode ( string $json [, bool $assoc = FALSE [, int $depth = 512 [, int $options = 0 ]]] ) : mixed

Takes a $json UTF-8 encoded, and converts it into a PHP variable. If the $assoc parameter is true, returned objects are converted into associative arrays. The $depth parameter works like the previous function. Therefore it sets the maximum depth, that must be greater than zero. And finally, the $options parameter is a bit-mask of JSON_BIGINT_AS_STRING, JSON_OBJECT_AS_ARRAY, JSON_THROW_ON_ERROR.


json_last_error_msg ( void ) : string

Returns the error STRING of the last json_encode() or json_decode() call.


json_last_error ( void ) : int

Returns the error CODE of the last json_encode() or json_decode() call.

  • JSON_ERROR_NONE – No error
  • JSON_ERROR_DEPTH – The maximum stack depth has been exceeded
  • JSON_ERROR_STATE_MISMATCH – Invalid or malformed JSON
  • JSON_ERROR_CTRL_CHAR – Control character error, possibly incorrectly encoded
  • JSON_ERROR_SYNTAX – Syntax error
  • JSON_ERROR_UTF8 – Malformed UTF-8 characters
  • JSON_ERROR_RECURSION – One or more recursive references in the value to be encoded
  • JSON_ERROR_INF_OR_NAN – One or more NAN or INF values in the value to be encoded
  • JSON_ERROR_UNSUPPORTED_TYPE – A value of a type that cannot be encoded was given
  • JSON_ERROR_INVALID_PROPERTY_NAME – A property name that cannot be encoded was given
  • JSON_ERROR_UTF16 – Malformed UTF-16 characters

The Examples

PHP Object

From PHP Object to JSON

$phpObj->name = "Joki";
$phpObj->age = 31;
$phpObj->country = "Spain";
$phpObj->website = "";

$phpJSON = json_encode($phpObj);

echo $phpJSON;
{"name":"Joki", "age":31, "country":"Spain", "website":""}

From JSON to PHP Object

$phpJson = '{"a":1,"b":2,"c":3,"d":4}';

$phpRes = json_decode($phpJson);

object(stdClass)#1 (4) {
   ["a"] => int(1)
   ["b"] => int(2)
   ["c"] => int(3)
   ["d"] => int(4)

PHP Array

From PHP Array to JSON

$phpArr = array("Joki", "Mary", "Luca", "Daniel");

$phpJSON = json_encode($phpArr);

echo $phpJSON;

From JSON to PHP Array

$phpJson = '{"a":1,"b":2,"c":3,"d":4}';

$phpRes = json_decode($phpJson, true);

array(4) {
   ["a"] => int(1)
   ["b"] => int(2)
   ["c"] => int(3)
   ["d"] => int(4)