Why isn't onclick working with my function?

Why isn't onclick working with my function?

I'm trying to make a true or false game in PHP/HTML for practice. I keep
changing things around to try to get it to work but nothing I try is
working.
function correct() {
echo "<center><b>You got it correct!</b> Good job, <u>your winning has
been added to the leaderboards.</u></center>";
}
function incorrect() {
echo "<center><b>You got it <i>wrong</i>.</b> Sorry for your loss,
<u>your loss has been added to the leaderboards.</u></center>";
}
if ($chooseQ == 0) {
echo"<center>...<br>";
echo"<a href='?true'>True</a> <a href='?false'>False</a></center>";
Any help?