json_last_error_msg()

	function json_last_error_msg() {
		// See https://core.trac.wordpress.org/ticket/27799.
		if ( ! function_exists( 'json_last_error' ) ) {
			return false;
		}

		$last_error_code = json_last_error();

		// Just in case JSON_ERROR_NONE is not defined.
		$error_code_none = defined( 'JSON_ERROR_NONE' ) ? JSON_ERROR_NONE : 0;

		switch ( true ) {
			case $last_error_code === $error_code_none:
				return 'No error';

			case defined( 'JSON_ERROR_DEPTH' ) && JSON_ERROR_DEPTH === $last_error_code:
				return 'Maximum stack depth exceeded';

			case defined( 'JSON_ERROR_STATE_MISMATCH' ) && JSON_ERROR_STATE_MISMATCH === $last_error_code:
				return 'State mismatch (invalid or malformed JSON)';

			case defined( 'JSON_ERROR_CTRL_CHAR' ) && JSON_ERROR_CTRL_CHAR === $last_error_code:
				return 'Control character error, possibly incorrectly encoded';

			case defined( 'JSON_ERROR_SYNTAX' ) && JSON_ERROR_SYNTAX === $last_error_code:
				return 'Syntax error';

			case defined( 'JSON_ERROR_UTF8' ) && JSON_ERROR_UTF8 === $last_error_code:
				return 'Malformed UTF-8 characters, possibly incorrectly encoded';

			case defined( 'JSON_ERROR_RECURSION' ) && JSON_ERROR_RECURSION === $last_error_code:
				return 'Recursion detected';

			case defined( 'JSON_ERROR_INF_OR_NAN' ) && JSON_ERROR_INF_OR_NAN === $last_error_code:
				return 'Inf and NaN cannot be JSON encoded';

			case defined( 'JSON_ERROR_UNSUPPORTED_TYPE' ) && JSON_ERROR_UNSUPPORTED_TYPE === $last_error_code:
				return 'Type is not supported';

			default:
				return 'An unknown error occurred';
		}
	}