i.e. I know it's possible to add code like the following to a layout handle XML file
<css src="foo/baz/bar.css"/> <link src="Magento_Sales::js/bootstrap/order-create-index.js"/>
What I'm curious about is do these layout directives have direct PHP equivalents? If so, what are they. If not, is there a reasonable technique for stabling reproducing their behavior via PHP?