php如何去掉二维数组中的key

<?php
header('content-type:text/html;charset=utf-8');   
$arr = array(
"a"=>1,
"b"=>2,
"c"=>array("c1"=>3,"c2"=>4,"c3"=>5,"c4"=>6),
"d"=>6,
"e"=>array("e1"=>7,"e2"=>8,"e3"=>9,"e4"=>10),
"f"=>10,
"g"=>array("g1"=>11,"g2"=>12,"g3"=>13)
);
echo "原二维数组：";
var_dump($arr);

$res=[];
foreach($arr as $v){
	if(is_array($v)){
		$res[]=array_values($v);
	}else{
		$res[]=$v;
	}
}
echo "去掉key（键名）的二维数组：";
var_dump($res);
?>