关于php递归函数的问题

<?phpfunction draw($total,$line=1,$result="a1"){    echo "<script>alert('$total,$line')</script>";	if($line>$total){        return;    }    else{        $line++;        //echo $result;        echo "<script>alert('draw1($total,$line,$result)')</script>";        draw($total,$line,$result);        echo "<script>alert('draw2($total,$line,$result)')</script>";	}	echo $result;}draw(3);?>

语句中执行函数draw(3)，当运行到if($line>$total){return;}echo出来三条信息draw2(3,4,a1)-->draw2(3,3,a1)-->draw2(3,2,a1)然后结束，请问是什么 原因使$line在return发生后，依次减1呢？

回复讨论(解决方案)

没有原因，因为他并没有变

function draw($total,$line=1,$result="a1"){    echo "<script>alert('$total,$line')</script>";    if($line>$total){        return;    }    else{        $line++;        //echo $result;        echo "<script>alert('draw1($total,$line,$result)')</script>";echo "递归前 line = $line\n";        draw($total,$line,$result);echo "递归后 line = $line\n";        echo "<script>alert('draw2($total,$line,$result)')</script>";    }    echo $result;}draw(3);

谢谢，我想我递归的原理还没弄明白，再去找下资料吧