NULL value for a property considered __isset false
@param mixed $key
@return $this
165033
function del($key)
    {
        if ($this->has($key)) {
            $p = &$this->__attainInternalPointer();
            unset($p[$key]);
        }

        return $this;
    }
661125
public function __isset($key)
    {
        if (parent::__isset($key) === true) {
            return true;
        }

        if (isset($this->viewBag[$key]) === true) {
            return true;
        }

        return isset($this->settings[$key]);
    }
1205390
public function del($key)
    {
        if (isset($this->value[$key])) {
            $t = $this->value[$key];
            unset($this->value[$key]);
            return $t;
        }

        return null;
    }
467384
public function has($key)
    {
        $value = $this->get($key);

        return ! is_null($value) && $value !== false;
    }
1119273
public function __isset($key)
    {
        if (isset($this->custom_attributes[$key]))
            return true;

        return ! is_null($this->getAttribute($key));
    }
429846
public function set($key, $value = null)
    {
        if( is_array($key) ) {
            $this->values($key);
        } else {
            $this->value($key, $value);
        }
        return $this;
    }
220930
public function remove($key) {
        if (isset($this->data[$key])) {
            $value = $this->data[$key];
            unset($this->data[$key]);
            return $value;
        } else {
            return null;
        }
    }
470994
public function isQuery($key = null)
    {
        $value = $this->request->get($key);

        return !empty($value);
    }
324833
public function get($key)
    {
        if (!$this->isEnabled()) {
            return null;
        }

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

        return false === $value ? null : $value;
    }
295874
public function __isset($key)
	{
		if (!$this->_isParsed)
		{
			$this->_parseData();
			$this->_isParsed = true;
		}

		return isset($this->_parsedData->$key);
	}
1061441
function delete($key) {
        $this->data[$key] = null;
        unset($this->data[$key]);
        return $this;
    }
129638
public function __isset($key)
    {
        if (!array_key_exists($key, $this->props)) {
            try {
                $this->__get($key);
            } catch (FieldNotExist $e) {
                return false;
            }
        }
        return true;
    }
76444
public function forget($key = null)
    {
        $this->startSession();

        if ($key === null) {
            unset($_SESSION[$this->session_key][$this->name]);
        } else {
            unset($_SESSION[$this->session_key][$this->name][$key]);
        }

        return $this;
    }
294186
public function has(?string $key = null) : bool
    {
        $key = $this->constructKey($key);

        return $this->parseKey($key, function ($part, $result) {
            return isset($result[$part]);
        });
    }
636651
public function __isset($key) {
        if (method_exists($this, 'get_'.$key)) {
            $val = $this->{'get_'.$key}();
            return !empty($val);
        }
        return !empty($this->properties->{$key});
    }
827459
public function has($key)
    {
        if (! $this->isNestedKey($key)) {
            return isset($this->items[$key]);
        } else {
            return ! is_null($this->getNestedValueByKey($key));
        }
    }
147979
public function key($key = null) {
		if($key === null) return $this->key;
		$this->key = $key;
		return $this;
	}