Get arg value for this field

@param	$key string The argument key
@return	string|integer|NULL The argument value
164647
public function arg($key) {
		return isset($this->args->$key) ? $this->args->$key : null;
	}
394796
protected function getField($key)
    {
        return !empty($this->response[$key]) ? $this->response[$key] : null;
    }
373213
public function getParamter($key)
    {
        return isset($this->params[$key]) ? $this->params[$key] : null;
    }
1364046
public function getArgument($key)
    {
        if (! array_key_exists($key, $this->arguments)) {
            throw new ErrorException('Undefined index: '.$key);
        }

        return $this->arguments[$key];
    }
968999
public function get($key = null)
    {
        if ($key) {

            if (isset($_GET[$key])) {
                return $_GET[$key];
            }

            throw new \InvalidArgumentException(sprintf(
                '%s ist not a valid key for $_GET', $key
            ));

        }

        return $_GET;
    }
1038622
public function getIntegerValue($key)
    {
        $value = $this->get($key);
        if ($value === null) {
            return null;
        }
        return (integer)$value;
    }
504113
public function getParam($key)
    {
        return null !== $this->getDraft() ? $this->getDraft()->getParam($key) : parent::getParam($key);
    }
838674
public function getQueryParam($key)
    {
        if (isset($this->queryParams[$key])) {
            return $this->queryParams[$key];
        }
        return null;
    }
902630
public function getArgument($key)
    {
        if ($this->hasArgument($key)) {
            return $this->arguments[$key];
        }

        throw new \InvalidArgumentException(sprintf('%s not found in %s', $key, $this->getName()));
    }
460279
private function getField($key)
    {
        return isset($this->data[$key]) ? $this->data[$key] : null;
    }
1038159
public function getValue($key, $default = null)
    {
        if (is_array($this->kwargs) && isset($this->kwargs[$key])) {
            return $this->kwargs[$key];
        }
        return $default; // @codeCoverageIgnore
    }
1050692
public function getValue($key) {
		if (isset ( $this->a [$key] )) {
			return $this->a [$key];
		} else {
			return NULL;
		}
	}
1069236
private function getValue ($key)
    {
        return isset($this->configuration[$key])
            ? $this->configuration[$key]
            : null;
    }
983168
protected function getHelpValue($key)
    {
        if (!isset($this->helpValues[$key])) {
            throw new \InvalidArgumentException(sprintf('The required help value "%s" doesn\'t exist.', $key));
        }

        return $this->helpValues[$key];
    }
755738
protected function getAttributeValue($key)
    {
        if (array_key_exists($key, $this->attributes)) {
            return $this->attributes[$key];
        }

        return null;
    }
827734
public function getParameter($key) {
    if (is_string($key)) {
      return $this->getParameterByName($key);
    }
    elseif (is_integer($key)) {
      return $this->getParameterAtIndex($key);
    }
    else {
      throw new \InvalidArgumentException("Illegal parameter index {$key}.");
    }
  }
496970
public function getArgs($key = NULL)
    {
        if (NULL === $key) {
            return $this->args;
        }

        if (!isset($this->args[$key])) {
            return;
        }

        return $this->args[$key];
    }