[php] 특정 배열요소 값을 순환식으로 교대로 얻기

<?
$cnoArr = array('12', '15', '17', '19', '21', '22', '23');
 
function getItemFor3($arr,&$i){
    $arr2 = array();
    $i++;
    $m = count($arr);
    $arr2[]=$arr[$i%$m];
    $arr2[]=$arr[(++$i)%$m];
    $arr2[]=$arr[(++$i)%$m];
    return $arr2;
}
 
$i = 1;
$arr = getItemFor3($cnoArr,$i);
 
var_dump($arr);
 
// array(3) { [0]=> string(2) "17" [1]=> string(2) "19" [2]=> string(2) "21" }
 
$i = 9;
$arr = getItemFor3($cnoArr,$i);
var_dump($arr);
 
// array(3) { [0]=> string(2) "19" [1]=> string(2) "21" [2]=> string(2) "22" }
?>