Php - get number, not char from string - php

Question

I'm not very familiar with php and got stuck in how to use substr in this case:
I have to do the parse of a string that has some numbers and symbols,
example:
1[2[3,5],4[7[65,9,11],8]]
And to do this I used a for that will go through and get each char of the string,
something like that:
$count = 0;
for($i = 0; $i <= strlen($string); $i++){
$char = substr($string, $i, 1);
if($char == '['){
$count --;
}
if($char == ']'){
$count ++;
}
if($count == 0){
break;
}
if(is_numeric(substr($string, $i +1, 1)) and $count == -1){
$number = substr($string, $i +1, 1);
$array_aux[] = $number;
}
}
But as I'm getting the char in (substr ($ string, $ i, 1)) it does not work for numbers with more than one digit, such as 65 and 11
And the contents of the array gets something like: (..., 6, 5, 9, 1, 1, ...)
When should be something like: (..., 65, 9, 11, ...)
Any help?
Sorry, I think was not clear enough.
I need the numbers that are inside '[' when count has the value -1
(that's why I'm using substr, and taking every char)
examples: when the string is: 1[2[3,5],4[7[65,9,11],8]], the array must contain 2 and 4
when the string is: 2[3,5],4[7[65,9,11],8]], the array must contain 3 and 5
when the string is: 7[65,9,11],8]], the array must contain 65, 9 and 11. And so on...
Sorry to put these details only now, I was without computer :(

Answer 1

preg_match_all with a simple regular expression can do this for you:
$in = "1[2[3,5],4[7[65,9,11],8]]";
preg_match_all('~\d+~', $in, $out);
print_r($out[0]);
Outputs:
Array
(
[0] => 1
[1] => 2
[2] => 3
[3] => 5
[4] => 4
[5] => 7
[6] => 65
[7] => 9
[8] => 11
[9] => 8
)

Answer 2

You can use preg_split and split by matching one or more times not a digit \D+
$str = "1[2[3,5],4[7[65,9,11],8]]";
print_r(preg_split("/\D+/", $str, -1, PREG_SPLIT_NO_EMPTY));
Array
(
[0] => 1
[1] => 2
[2] => 3
[3] => 5
[4] => 4
[5] => 7
[6] => 65
[7] => 9
[8] => 11
[9] => 8
)