functions.php

<?php

if (!function_exists('utf8_sanitize')) {
    function utf8_sanitize($mixed)
    {
        if (is_array($mixed)) {
            foreach ($mixed as $key => $value) {
                $mixed[$key] = utf8_sanitize($value);
            }
        } elseif (is_object($mixed)) {
            foreach ($mixed as $key => $value) {
                $mixed->{$key} = utf8_sanitize($value);
            }
        } elseif (is_string($mixed)) {
            return mb_convert_encoding($mixed, "UTF-8", "UTF-8");
        }

        return $mixed;
    }
}

if (!function_exists('json_safe_encode')) {
    function json_safe_encode($object, $flags = null)
    {
        if (defined('JSON_INVALID_UTF8_IGNORE')) {
            $flags |= JSON_INVALID_UTF8_IGNORE;
        } else {
            $object = utf8_sanitize($object);
        }

        $flags |= JSON_PRETTY_PRINT;
        $flags |= JSON_UNESCAPED_SLASHES;

        $json = json_encode($object, $flags);

        if ($json === false) {
            $json = json_encode([
                'json_last_error' => json_last_error(),
                'json_last_error_msg' => json_last_error_msg(),
                'trace' => debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS)
            ], JSON_PRETTY_PRINT);
        }

        return $json;
    }
}