public function docType($type = 'html5')
    {
        if (isset($this->_docTypes[$type])) {
            return $this->_docTypes[$type];
        }

        return null;
    }
public function docType($type = 'html5')
    {
        if (isset($this->_docTypes[$type])) {
            return $this->_docTypes[$type];
        }

        return null;
    }
public function docType ( $ type = 'html5' ) { if ( isset ( $ this -> _docTypes [ $ type ] ) ) { return $ this -> _docTypes [ $ type ] ; } return null ; }
Returns a doctype string.

Possible doctypes:

- html4-strict:  HTML4 Strict.
- html4-trans:  HTML4 Transitional.
- html4-frame:  HTML4 Frameset.
- html5: HTML5. Default value.
- xhtml-strict: XHTML1 Strict.
- xhtml-trans: XHTML1 Transitional.
- xhtml-frame: XHTML1 Frameset.
- xhtml11: XHTML1.1.

@param string $type Doctype to use.
@return string|null Doctype string
@link https://book.cakephp.org/3.0/en/views/helpers/html.html#creating-doctype-tags
Returns a doctype string .