Well, I feel like I've tried every possible thing that can be tried with PHP, so I eventually went with JSObject. Now THAT was easy.
Working Java code:
JSObject window = JSObject.getWindow(this);
// invoke JavaScript function
String result = "<table><tr><th>Column1</th><th>Column2</th></tr><tr><td>"
+ field1 + "</td><td>" + field2 + "</td></tr></table>";
window.call("writeResult", new Object[] {result});
Relevant working Javascript:
function writeResult(result) {
var resultElem =
document.getElementById("anHTMLtagID");
resultElem.innerHTML = result;
}
From here I can even send the results from Javascript to PHP via Ajax to do database-related actions. Yay!