public static function isOptionalExistingKey($key, array $values)
    {
        /* No additional validations when the value is null. */
        if (null === $key) {

            return true;
        }

        return self::isRequiredExistingKey($key, $values);
    }
public static function isOptionalExistingKey($key, array $values)
    {
        /* No additional validations when the value is null. */
        if (null === $key) {

            return true;
        }

        return self::isRequiredExistingKey($key, $values);
    }
public static function isOptionalExistingKey ( $ key , array $ values ) { /* No additional validations when the value is null. */ if ( null === $ key ) { return true ; } return self :: isRequiredExistingKey ( $ key , $ values ) ; }
Optional key exists.

@param string $key    Key to check.
@param array  $values Array in which to search.

@return bool
Optional key exists .