Using "if" is the best way, of course. I'd say to use arrays, for both your form checkboxes and your follow-up questions (whether fetched from a text file or a database). Then you could use one loop to find the checked values and to display the questions:
// First page:
echo '<form action="' . $_SERVER['PHP_SELF'] . '" method="post">' .
'<input type="checkbox" name="check[please_contact]" />' .
'<input type="checkbox" name="check[repair_only]" />' .
'<input type="submit" name="submit" value="Submit" />' .
'</form>';
// Follow-up page:
if (isset($_POST['check'])) {
foreach ($_POST['check'] as $key => $value) {
echo $follow_up_questions[$key];
}
} else {
echo 'Nothing checked' . '<br />';
}
Sorry for posting code; it's my best way of explaining. Many find that reading code is a good way to learn. hth