[PHP]遞迴呼叫-階層

< ?php
function factory($n)
{//判定是否為整數且大於零
if(is_integer($n) && $n>0){
if($n>=2){
$temp=$n ;
$n=$n-1;
//遞迴呼叫本身
$total=$temp * factory($n);
return $total;
}else{
return 1;
}
}else{
echo "請輸入大於零的整數";
}
}

//呼叫factory 函數
echo "5! = ".factory(5)."< br/>";
echo "6! = ".factory(6)."< br/>";
echo "7! = ".factory(7)."< br/>";
? >