PHP版：
复制代码 代码如下:
$o = array("x"=>1, "y"=>2, "z"=>3);
$arr = array();
$i = 0;
foreach( $o as $arr[$i++]=>$v )/*empty*/;
var_dump($arr); //$arr = array("x", "y", "z");

JavaScrip版：
复制代码 代码如下:
var o = {x:1, y:2, z:3};
var arr = [], i = 0;
for ( arr[i++] in o ) /*empty*/ ;
console.log( arr ); //arr = ["x", "y", "z"];