我有一个数组如下：

function example() {
    /* some stuff here that pushes items with
        dynamically created key strings into an array */

    return array( // now lets pretend it returns the created array
        'firstStringName' => $whatEver,
        'secondStringName' => $somethingElse
    );
}

$arr = example();

// now I know that $arr contains $arr['firstStringName'];

我需要找出的索引，$arr['firstStringName']以便能够遍历array_keys($arr)并'firstStringName'通过其索引返回键字符串。我怎样才能做到这一点？