Seldaek/monolog · error · RuntimeException

JSON encoding failed: {}. Encoding: {}

Error message

JSON encoding failed: {}. Encoding: {}

What it means

Error "JSON encoding failed: {}. Encoding: {}" thrown in Seldaek/monolog.

Source

Thrown at src/Monolog/Utils.php:160

    /**
     * Throws an exception according to a given code with a customized message
     *
     * @param  int               $code return code of json_last_error function
     * @param  mixed             $data data that was meant to be encoded
     * @throws \RuntimeException
     */
    private static function throwEncodeError(int $code, $data): never
    {
        $msg = match ($code) {
            JSON_ERROR_DEPTH => 'Maximum stack depth exceeded',
            JSON_ERROR_STATE_MISMATCH => 'Underflow or the modes mismatch',
            JSON_ERROR_CTRL_CHAR => 'Unexpected control character found',
            JSON_ERROR_UTF8 => 'Malformed UTF-8 characters, possibly incorrectly encoded',
            default => 'Unknown error',
        };

        throw new \RuntimeException('JSON encoding failed: '.$msg.'. Encoding: '.var_export($data, true));
    }

    /**
     * Detect invalid UTF-8 string characters and convert to valid UTF-8.
     *
     * Valid UTF-8 input will be left unmodified, but strings containing
     * invalid UTF-8 codepoints will be reencoded as UTF-8 with an assumed
     * original encoding of ISO-8859-15. This conversion may result in
     * incorrect output if the actual encoding was not ISO-8859-15, but it
     * will be clean UTF-8 output and will not rely on expensive and fragile
     * detection algorithms.
     *
     * Function converts the input in place in the passed variable so that it
     * can be used as a callback for array_walk_recursive.
     *
     * @param mixed $data Input to check and convert if needed, passed by ref
     */
    private static function detectAndCleanUtf8(&$data): void

View on GitHub (pinned to 57eb102834)

When it happens

Trigger: Thrown at src/Monolog/Utils.php:160 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of Seldaek/monolog@57eb102834 (2026-08-17). Data as JSON: /api/errors/6270fb322c17d982. Report an issue: GitHub.