在第18个位置分割字符串.然后在数组第10个位置的每个值上添加空格.

Split string on every 18th position. Then add space on every value of the array on 10th position.

$k = "2013-01-0112:00:002013-01-0212:00:002013-01-0312:00:00";
$a = str_split($k, 18);
$a = array_map(function($dt) {
    return implode(' ', str_split($dt, 10));
}, $a);
print_r($a);

演示 .

Demo.

如果要将字符添加到第N个位置:

If you wish to add character to N-th position:

$k = "2013-01-0112:00:002013-01-0212:00:002013-01-0312:00:00";
echo implode(',', str_split($k, 18));
//            ^                  ^
//        character         N-th position

演示 .

Demo.