In it's current state, the Zend_Json_Server_Response class does not contain a way to find Zend_Json_Expr objects when returning data (with the toJson method, called automatically by default by Zend_Json_Server).

It would be very helpful to have a "findJsonExpr" flag within the Zend_Json_Server_Response class, that would be either true or false by default depending on the performance-wise implications such functionality brings.

The current public method toJson has the following implementation:

/**
     * Cast to JSON
     *
     * @return string
     */
    public function toJson()
    {
        if ($this->isError()) {
            $response = array(
                'result' => null,
                'error'  => $this->getError()->toArray(),
                'id'     => $this->getId(),
            );
        } else {
            $response = array(
                'result' => $this->getResult(),
                'id'     => $this->getId(),
                'error'  => null,
            );
        }

        if (null !== ($version = $this->getVersion())) {
            $response['jsonrpc'] = $version;
        }

        require_once 'Zend/Json.php';
        return Zend_Json::encode($response);
    }

Proposal:

/**
     * Cast to JSON
     *
     * @return string
     */
    public function toJson()
    {
        if ($this->isError()) {
            $response = array(
                'result' => null,
                'error'  => $this->getError()->toArray(),
                'id'     => $this->getId(),
            );
        } else {
            $response = array(
                'result' => $this->getResult(),
                'id'     => $this->getId(),
                'error'  => null,
            );
        }

        if (null !== ($version = $this->getVersion())) {
            $response['jsonrpc'] = $version;
        }

        require_once 'Zend/Json.php';
        return Zend_Json::encode($response, false, array("findJsonExpr" => $this->_findJsonExpr)); //_findJsonExpr is a protected member (bool)
    }

Right now, I have to disable auto-emit in Zend_Json_Server, retrieve the response object and do the whole routine above after sending the correct headers, with the exception of the last line.