php字符怎么转化成字节数组

$str = "Hello World";$bytes = str_split($str);print_r($bytes);

Array (    [0] => H    [1] => e    [2] => l    [3] => l    [4] => o    [5] =>    [6] => W    [7] => o    [8] => r    [9] => l    [10] => d)

$str = "Hello World";$bytes = unpack('C*', $str);print_r($bytes);

Array(    [1] => 72    [2] => 101    [3] => 108    [4] => 108    [5] => 111    [6] => 32    [7] => 87    [8] => 111    [9] => 114    [10] => 108    [11] => 100)

$str = "你好世界";$bytes = preg_split('//u', $str, -1, PREG_SPLIT_NO_EMPTY);foreach($bytes as &$byte) {    $byte = bin2hex(mb_convert_encoding($byte, 'UCS-2BE'));}print_r($bytes);

Array (    [0] => 4f60    [1] => 597d    [2] => 4e16    [3] => 754c)