<form method="post" action="">
<input type="text" name="num" size="5">
<input type="submit" value="計算">
</form>
<?php
function aaa($a){
print $a;
$a--;
if($a>=1){
print " x ";
aaa($a);
}
}
if(isset($_POST['num']) AND $_POST['num']!=""){
$ccc=$_POST['num'];
$ddd = htmlspecialchars($ccc,ENT_QUOTES,"UTF-8");
aaa($ddd);
}
?>