PHP如何将数组里字符串转为数组

$arr = ['1.a.d.f.g.r.t', '1.2.3.4.5.6.7.8.9', '0.a.1.r.g.k.5'];

$arr = implode('.', $arr);

$arr = explode('.', $arr);

var_dump($arr);

array(23) { 
[0]=> 
string(1) "1" 
[1]=> 
string(1) "a" 
[2]=> 
string(1) "d" 
[3]=> 
string(1) "f" 
[4]=> 
string(1) "g" 
[5]=> 
string(1) "r" 
[6]=> 
string(1) "t" 
[7]=> 
string(1) "1" 
[8]=> 
string(1) "2" 
[9]=> 
string(1) "3" 
[10]=> 
string(1) "4" 
[11]=> 
string(1) "5" 
[12]=> 
string(1) "6" 
[13]=> 
string(1) "7" 
[14]=> 
string(1) "8" 
[15]=> 
string(1) "9" 
[16]=> 
string(1) "0" 
[17]=> 
string(1) "a" 
[18]=> 
string(1) "1" 
[19]=> 
string(1) "r" 
[20]=> 
string(1) "g" 
[21]=> 
string(1) "k" 
[22]=> 
string(1) "5" 
}