在while循环中的每次迭代中将一个计数加到动态数组键

Hi I am making a polling functionality. In the below code I am trying to get count of answers by storing the key of array $count as id of the answer and += to count how many times it was chosen as an answer.

The problem that I am having is that $count[$option_id] += 1; doesn't work. Not sure what I am doing wrong with the logic. In the database the records exist and I can confirm that query run fine and gets the result.

There are 2 answers possible per vote. For eg: lets take answer with Id 1 and 2. So, in the end, it should output something like

details: {1: 20, 2: 50}

This means that 20 people have voted for Answer 1 and 50 people for 2.

Any help will be great, Thanks

$answer_count = 0;
$count = array();

$query = "SELECT * FROM `votes` where ques_id = 55";
$stmt = $this->db_obj->query_exec($query);

while($info = mysqli_fetch_array($stmt)){
    $answer_count++;
    $option_id = $info['option_id'];
    $count[$option_id] += 1;
}
return json_encode(array("success" => "1","total" => $answer_count,"details" => $count));