src/CanvasArray.php
public function offsetExists($offset)
    {
        if (!isset($this->data[$offset])) {
            $this->requestAllPages();
        }
        return isset($this->data[$offset]);
    }
public function offsetExists($offset)
    {
        if (!isset($this->data[$offset])) {
            $this->requestAllPages();
        }
        return isset($this->data[$offset]);
    }
Whether an offset exists

@param int|string $offset

@return bool

@see http://php.net/manual/en/arrayaccess.offsetexists.php
ArrayAccess::offsetExists