src/datetime/OrderedList.php
public function offsetExists($offset)
    {
        if (!$offset instanceof Date) {
            $offset = new Date($offset);
        }

        $item = $this->searchOffset($offset);
        return is_null($item) ? false : true;
    }
public function offsetExists($offset)
    {
        if (!$offset instanceof Date) {
            $offset = new Date($offset);
        }

        $item = $this->searchOffset($offset);
        return is_null($item) ? false : true;
    }
(PHP 5 &gt;= 5.1.0)<br/>
Whether a offset exists
@link http://php.net/manual/en/arrayaccess.offsetexists.php
@param mixed $offset <p>
An offset to check for.
</p>
@return boolean Returns true on success or false on failure.
</p>
<p>
The return value will be casted to boolean if non-boolean was returned.