helpers.php

<?php

if (!function_exists('json_last_error_msg')) {
    function json_last_error_msg()
    {
        switch (json_last_error()) {
            case JSON_ERROR_DEPTH:
                return 'The maximum stack depth has been exceeded';
            case JSON_ERROR_STATE_MISMATCH:
                return 'Invalid or malformed JSON';
            case JSON_ERROR_CTRL_CHAR:
                return 'Control character error, possibly incorrectly encoded';
            case JSON_ERROR_SYNTAX:
                return 'Syntax error';
            case JSON_ERROR_UTF8:
                return 'Malformed UTF-8 characters, possibly incorrectly encoded';
            case JSON_ERROR_RECURSION:
                return 'One or more recursive references in the value to be encoded';
            case JSON_ERROR_INF_OR_NAN:
                return 'NAN or INF values in the value to be encoded';
            case JSON_ERROR_UNSUPPORTED_TYPE:
                return 'A value of a type that cannot be encoded was given';
        }
    }
}