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"    
}