public function isMissing($option)
    {
        return isset($this->required[$option]) && !\array_key_exists($option, $this->defaults);
    }
public function isMissing($option)
    {
        return isset($this->required[$option]) && !\array_key_exists($option, $this->defaults);
    }
public function isMissing ( $ option ) { return isset ( $ this -> required [ $ option ] ) && ! \ array_key_exists ( $ option , $ this -> defaults ) ; }
Returns whether an option is missing a default value.

An option is missing if it was passed to {@link setRequired()}, but not
to {@link setDefault()}. This option must be passed explicitly to
{@link resolve()}, otherwise an exception will be thrown.

@param string $option The name of the option

@return bool Whether the option is missing
Returns whether an option is missing a default value .