gchq/CyberChef · error · OperationError

Encountered a non-implemented type: ${typeof content}

Error message

Encountered a non-implemented type: ${typeof content}

What it means

The serializeBasicTypes() function handles boolean, number, and string. If none match (the value is a BigInt, Symbol, undefined, or function disguised as a primitive), this 'should be unreachable' throw fires. It is a defensive guard for types the serializer was never designed to handle at the leaf level.

Source

Thrown at src/core/operations/PHPSerialize.mjs:77

             * cast to 0 or 1
             */
            if (typeof content === "boolean") {
                return `${basicTypes.boolean}:${content ? 1 : 0}`;
            }
            /* Numbers */
            if (typeof content === "number") {
                if (isInteger(content)) {
                    return `${basicTypes.integer}:${content.toString()}`;
                } else {
                    return `${basicTypes.float}:${content.toString()}`;
                }
            }
            /* Strings */
            if (typeof content === "string")
                return `${basicTypes.string}:${content.length}:"${content}"`;

            /** This should be unreachable */
            throw new OperationError(`Encountered a non-implemented type: ${typeof content}`);
        }

        /**
         * Recursively serialize
         * @param {*} object
         * @returns {string}
         */
        function serialize(object) {
            /* Null */
            if (object == null) {
                return `N;`;
            }

            if (typeof object !== "object") {
                /* Basic types */
                return `${serializeBasicTypes(object)};`;
            } else if (object instanceof Array) {
                /* Arrays */

View on GitHub (pinned to 4290ea7539)

Solutions

  1. Ensure all leaf values in the JSON input are plain booleans, numbers, or strings
  2. Convert BigInt values to regular numbers or strings before passing them in
  3. Remove or stringify any Symbol-keyed or Symbol-valued properties

Example fix

// before
const data = { id: BigInt(123), name: "test" };
// after
const data = { id: Number(123), name: "test" };
Defensive patterns

Strategy: type-guard

Validate before calling

// Pre-check: ensure no unsupported primitive types
function hasUnsupportedPrimitives(obj) {
  for (const v of Object.values(obj)) {
    if (typeof v === 'bigint' || typeof v === 'symbol') return true;
    if (typeof v === 'object' && v !== null) {
      if (hasUnsupportedPrimitives(v)) return true;
    }
  }
  return false;
}

Type guard

function isSerializablePrimitive(v) {
  return typeof v === 'boolean' || typeof v === 'number' || typeof v === 'string';
}

Try / catch

try {
  const result = chef.phpSerialize(input);
} catch (e) {
  if (/non-implemented type/i.test(e.message)) {
    console.error("Unsupported primitive type — convert BigInts/Symbols to strings or numbers");
  } else { throw e; }
}

Prevention

When it happens

Trigger: A JSON value that is a Symbol or BigInt reaches serializeBasicTypes because typeof returns 'symbol' or 'bigint', neither of which matches the boolean/number/string branches. A function value whose typeof is 'function' could also reach here if it bypasses the object check upstream.

Common situations: Input JSON contains a BigInt (typeof 'bigint') or Symbol (typeof 'symbol'). A JSON revival function injected non-standard primitive types. The operation is called programmatically with a parsed JSON object containing non-JSON-safe values.

Related errors

AI-assisted analysis of gchq/CyberChef@4290ea7539 (2026-08-13). Data as JSON: /api/errors/868f2bedcb5c37d9. Report an issue: GitHub.