PHPの再帰関数に関する質問

<?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);?>

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);