<?php
$_REQUEST['mykey'] = '123';
$method = 'REQUEST';
$key = 'mykey';
echo $modx->request->parameters[$method][$key];

123

$scriptProperties['method'] = 'GET';
$modx->runProcessor('modcaptcha/web/check', $scriptProperties, array(
    'processors_path' => $path.'processors/',
))

function __construct(modX & $modx,array $properties = array()) {
        $this->modx =& $modx;
        $this->setProperties($properties);
    }

public function setDefaultProperties(array $properties = array()) {
        $this->properties = array_merge($properties,$this->properties);
        return $this->properties;
    }

$code = $modx->request->getParameters($key, strtoupper($method));