C#中UTF8Encoding.UTF8.GetBytes（key）,对应PHP中的哪个方法？如何写

$s = '中文abc';
$s = iconv('gbk', 'utf-8', $s); //不是 utf-8 时需转 utf-8
print_r(unpack('C*', $s));

Array
(
    [1] => 228
    [2] => 184
    [3] => 173
    [4] => 230
    [5] => 150
    [6] => 135
    [7] => 97
    [8] => 98
    [9] => 99
)

            foreach (var c in UTF8Encoding.UTF8.GetBytes("中文abc"))
            {
                Console.WriteLine(c);
            }

$s = '中文abc';
$s = iconv('gbk', 'utf-8', $s); //不是 utf-8 时需转 utf-8
print_r(unpack('C*', $s));

Array
(
    [1] => 228
    [2] => 184
    [3] => 173
    [4] => 230
    [5] => 150
    [6] => 135
    [7] => 97
    [8] => 98
    [9] => 99
)

            foreach (var c in UTF8Encoding.UTF8.GetBytes("中文abc"))
            {
                Console.WriteLine(c);
            }