public function offsetExists($offset)
    {
        if (!is_int($offset) && !is_string($offset)) {
            throw new RuntimeException('Invalid array offset type: '. gettype($offset));
        }
        return array_key_exists($offset, $this->items);
    }
public function offsetExists($offset)
    {
        if (!is_int($offset) && !is_string($offset)) {
            throw new RuntimeException('Invalid array offset type: '. gettype($offset));
        }
        return array_key_exists($offset, $this->items);
    }
public function offsetExists ( $ offset ) { if ( ! is_int ( $ offset ) && ! is_string ( $ offset ) ) { throw new RuntimeException ( 'Invalid array offset type: ' . gettype ( $ offset ) ) ; } return array_key_exists ( $ offset , $ this -> items ) ; }
Tells whether or not an offset exists.

@param mixed $offset

@return boolean

@see http://php.net/manual/en/class.arrayaccess.php
Tells whether or not an offset exists .