您需要同时检查两个项目。下面是你如何做到这一点的例子。

// making a Generator, that will return pair of elements on each iteration
function fetchPairs($result) {
  // initialize array, which will store elements
  $pair = [];
  while ($row = mysqli_fetch_array($result)) {
    // add each element in array
    $pair[] = $row;
    // if there is 2 elements..
    if (count($pair) === 2) {
      // ..yield them and..
      yield $pair;
      // ..clear array
      $pair = [];
    }
  }
}

$count = 0;
// in this `foreach` each iteration now returns pair of two elements;
foreach (fetchPairs($res) as [$first, $second]) { // you can use $pair instead of destructing list into $first and $second varialbes
   // check both items are 'vincente'
   if ($first['result'] === 'vincente' && $second['result'] === 'vincente') {
      $count += 1;
   }
}