useless.php

<?php
// or just use json_last_error_msg...
public function get_json_human_error($err_code)
    {
        $constants            = get_defined_constants(true);
        $json_error_constants = array_filter(array_keys($constants['json']), function($row) {
            return strpos($row, 'JSON_ERROR_') !== false;
        });
        foreach ($json_error_constants as $index => $error_name) {
            $json_error_constants[constant($error_name)] = $error_name;
            unset($json_error_constants[$index]);
        }
        return isset($json_error_constants[$err_code]) ? $json_error_constants[$err_code] : 'UNKNOWN_JSON_ERROR';
    }