PHP如何把字符串转换为数组

$str = "Hello";$arr = str_split($str);print_r($arr);

Array(    [0] => H    [1] => e    [2] => l    [3] => l    [4] => o)

$str = "apple,orange,banana";$arr = explode(",", $str);print_r($arr);

$str = "apple1orange2banana";$arr = preg_split("/d+/", $str);print_r($arr);

$str = "Hello world!";$arr = str_word_count($str, 1);print_r($arr);

Array(    [0] => Hello    [1] => world)

$str = "123456789";$arr = str_split($str, 2);print_r($arr);

Array(    [0] => 12    [1] => 34    [2] => 56    [3] => 78    [4] => 9)

$str = "hello";$arr = str_split(str_repeat($str, 3), strlen($str));print_r($arr);

Array(    [0] => h    [1] => e    [2] => l    [3] => l    [4] => o    [5] => h    [6] => e    [7] => l    [8] => l    [9] => o    [10] => h    [11] => e    [12] => l    [13] => l    [14] => o)