PHP How to keep radio button state to the next page

PHP How to keep radio button state to the next page

I made a form with radio buttons. How can I preserve it's state after a
user picked a choice? Then same form will show again in the next page and
the radio button that the user picked is enabled.
//page1.html
<form method="post" action="page2.html">
<p>
<input type="radio" name="q1" value="A" />
A. <br />
<input type="radio" name="q1" value="B" />
B. <br />
<input type="radio" name="q1" value="C" />
C. <br />
<input type="radio" name="q1" value="D" />
D.
<p>
<input type="submit" name="action" value="Enter" />
</p>
</form>