/**
 * The Much easier way is to use array_diff_key
 * 用数组的键过滤数关联组
 * @param array $arr ['k1' => 'va1', 'k2' => 'va2', 'k3' => 'va3']
 * @param string $keyStr 'k1,k2'
 * @param string $type  'include|exclude'
 * @return unknown[]
 */
function filter_array_by_key($arr, $keyStr, $type = 'include') {
    $result = [];
    $keys = explode(',', $keyStr);
    if (strtolower($type) == 'include') {
        foreach ($keys as $k) {
            if (isset($arr[$k])) $result[$k] = $arr[$k];
        }
    }

    if (strtolower($type) == 'exclude') {
        foreach ($arr as $k => $v) {
            if (!in_array($k, $keys)) {
                $result[$k] = $v;
            }
        }
    }

    return $result;
}