Retrieves all parameters if no key is specified

@param string|null $key

@return string|array
760091
private function getExportParams($key = null)
    {
        if ($key && isset($this->exportParams[$key])) {
            return $this->exportParams[$key];
        }

        return $this->exportParams;
    }
107389
public function getUrlParam($key)
    {
        $pa = $this->getUrlParams();
        return isset($pa[$key]) ? $pa[$key] : null;
    }
376063
public function offsetGet( $key )
    {
        $key = strtolower( $key );
        if ( !array_key_exists( $key, $this->lookup ) )
        {
            return null;
        }
        return $this->map[$this->lookup[$key]];
    }
1084695
public function getParam($key)
    {
        return isset($this->_rawRequest[$key]) ? $this->_rawRequest[$key] : null;
    }
105136
function &get($key) {
		if (isset($this->args[$key]))
			$val=&$this->args[$key];
		else
			$val=NULL;
		return $val;
	}
324833
public function get($key)
    {
        if (!$this->isEnabled()) {
            return null;
        }

        $value = $this->server->get($this->prefix . $key);

        return false === $value ? null : $value;
    }
164039
public function getArray($key)
	{
		$this->validateKey($key);
		return $this->has($key) ? $this->params[$key] : [];
	}
472883
public function getParameter($key)
    {
        if(isset($this->queryParts[$key])) {
            return $this->queryParts[$key];
        } else {
            return false;
        }
    }
104795
private function getParam($key)
    {
        if (!$this->getParams) {
            $this->getParams = filter_input(INPUT_GET, self::UKEY1_GET_PARAM, FILTER_DEFAULT, FILTER_REQUIRE_ARRAY);
        }
        
        if (isset($this->getParams[$key]) && $this->getParams[$key] && (is_string($this->getParams[$key]) || is_numeric($this->getParams[$key]))) {
            return $this->getParams[$key];
        } else {
            return "";
        }
    }
74589
public static function param($key = ''){
		if($key){
			$get = self::get();
			$post = self::post();
			if(isset($post[$key])){
				return $post[$key] ;
			}else if(isset($get[$key])){
				return $get[$key] ;
			}else{
				return "";
			}
		}else{
			$get = self::get();
			$post = self::post();
			return array_merge($get,$post);
		}
	}
20749
public function getParameter($key)
    {
        $filteredParameters = $this->parameters->filter(
            static function (Query\Parameter $parameter) use ($key) : bool {
                $parameterName = $parameter->getName();

                return $key === $parameterName || (string) $key === (string) $parameterName;
            }
        );

        return $filteredParameters->isEmpty() ? null : $filteredParameters->first();
    }
503285
public function getParameter($key)
    {
        $filteredParameters = $this->parameters->filter(
            function ($parameter) use ($key)
            {
                // Must not be identical because of string to integer conversion
                return ($key == $parameter->getName());
            }
        );

        return count($filteredParameters) ? $filteredParameters->first() : null;
    }
373213
public function getParamter($key)
    {
        return isset($this->params[$key]) ? $this->params[$key] : null;
    }
261462
protected function get($key)
    {
        $this->checkForNonEmptyKey($key);
        if (!$this->settingsHaveBeenRetrieved) {
            $this->retrieveSettings();
        }
        if (!isset($this->cachedSettings[$key])) {
            return null;
        }

        return $this->cachedSettings[$key];
    }
999654
public function getParam($key = null, $default = null)
    {
        if (null === $key) {
            return $this->data[self::P_PARAMS];
        }

        return $this->hasParam($key) ? $this->data[self::P_PARAMS][$key] : $default;
    }
1214596
public function keys(?string $key = null) : array
    {
        $value = $this->get($key);

        if (!is_array($value)) {
            throw new InvalidArgumentException(
                'method keys() should be called on array'
            );
        }

        return array_keys($value);
    }
211439
public function key($key = null)
    {
        if (!func_num_args()) {
            return $this->_key;
        }
        $this->_key = $key;
        return $this;
    }