(PHP 5 >= 5.3.0, PHP 7) Returns the last error occurred

(PHP 5 >= 5.2.0, PECL json >= 1.2.0, PHP 7) Decodes a JSON string

(PHP 5 >= 5.5.0, PHP 7) Returns the error string of the last json_encode() or json_decode() call

(PHP 5 >= 5.2.0, PECL json >= 1.2.0, PHP 7) Returns the JSON representation of a value