This is a piece of code of a new example that will be included in phpdocx pro 2.2 that do this feature:
$paramsHeaderTextTable[0] = array(
'text' => 'Text',
'b' => 'single',
'sz' => 14
);
$table[] = array(
$docx->addElement('addText', $paramsHeaderTextTable),
'Value 2',
'Value 3',
);
Regards.