Kozlov

if($result->num_rows > 0){
    $data = array();
    while ($row = $result->fetch_assoc()){
        $data[] = json_decode($row['data'], true);
    }
}
$i = 0;
    foreach ($data as $key => $value) {
       if ($data[$key]['q1'] == 'a1') {
        $i++;
       }
    }
echo $i;

$data = array();
if($result->num_rows > 0){
    while ($row = $result->fetch_assoc()){
        $data[] = json_decode($row['data'], true);
    }
}
function jsonCount($question, $answer){
    global $data;
    $i = 0;
    foreach ($data as $key => $value) {
       if ($data[$key][$question] == $answer) {
        $i++;
       }
    }
return $i;
}
echo jsonCount('q1', 'a1');
echo '<br>';
echo jsonCount('q1', 'a2');