<?php
function str_split_unicode($str, $l = 0) {
    return preg_split('/(.{'.$l.'})/us', $str, -1, PREG_SPLIT_NO_EMPTY|PREG_SPLIT_DELIM_CAPTURE);
}

$array = str_split_unicode("¿Habla usted español?");
print_r($array);

echo "<hr>";
while (list($i, $v) = each($array)) {
    echo "$i , $v<br>";
}
echo "<hr>";
foreach ($array as $i => $v) {
    echo "$i , $v<br>";
}

echo "<hr>";
$array = array("A" => "papá", "B" => "tendré", "C" => "cereza", "Ch" => "leche", "Ñ" => "niño", "R" => "rojo");
while (list($i, $v) = each($array)) {
    echo "$i , $v<br>";
}
?>

运行结果：
Array ( [0] => ¿ [1] => H [2] => a [3] => b [4] => l [5] => a [6] => [7] => u [8] => s [9] => t [10] => e [11] => d [12] => [13] => e [14] => s [15] => p [16] => a [17] => ñ [18] => o [19] => l [20] => ? ) 0 , ¿
1 , H
2 , a
3 , b
4 , l
5 , a
6 ,
7 , u
8 , s
9 , t
10 , e
11 , d
12 ,
13 , e
14 , s
15 , p
16 , a
17 , ñ
18 , o
19 , l
20 , ?
0 , ¿
1 , H
2 , a
3 , b
4 , l
5 , a
6 ,
7 , u
8 , s
9 , t
10 , e
11 , d
12 ,
13 , e
14 , s
15 , p
16 , a
17 , ñ
18 , o
19 , l
20 , ?
A , papá
B , tendré
C , cereza
Ch , leche
Ñ , niño
R , rojo

可见，while (list($i, $v) = each($array)) 与 foreach ($array as $i => $v) 完全等价。$i既可能是数字，也可能是字符串。