public function offsetExists($key)
    {
        $this->checkKey($this->key_type, $key);
        return isset($this->container[$key]);
    }
public function offsetExists($key)
    {
        $this->checkKey($this->key_type, $key);
        return isset($this->container[$key]);
    }
public function offsetExists ( $ key ) { $ this -> checkKey ( $ this -> key_type , $ key ) ; return isset ( $ this -> container [ $ key ] ) ; }
Check the existence of the element at the given key.

This will also be called for: isset($arr)

@param object $key The key of the element to be removed.
@return bool True if the element at the given key exists.
@throws \ErrorException Invalid type for key.
Check the existence of the element at the given key .