$handle = fopen (, );
$maxcount = 0;
$count = 0;
$times = array();
while (!feof($handle)) {
    $buffer = fgets($handle);
    $op = trim(substr($buffer,8,3));
    switch ($op){
        case 'IN':
            $count--;
        break;
        case 'OUT':
            $count++;
            preg_match('/([\d|\/|_|:]+)/',$buffer,$time);
            if($count>$maxcount){
                $maxcount = $count;
                $times = Array($time[0]);
            }elseif($count == $maxcount){
                $times[] = $time[0];
            }
        break;
    }   
}
fclose ($handle);

echo $maxcount . '<br>';
for($i=0;$i<count($times);$i++){
    echo $times[$i] . '<br>';
}