如您的错误所示，explode 需要一个分隔符来拆分字符串.使用 str_split 代替:

As indicated by your error, explode requires a delimiter to split the string. Use str_split instead:

$arr = str_split('testing');

输出

Array
(
    [0] => t
    [1] => e
    [2] => s
    [3] => t
    [4] => i
    [5] => n
    [6] => g
)