PHP循环 - 检查每一次循环中

Question

我想一个类添加到项目中在我的循环，每次是第二项有它上面的环形项目，所以像这样：

loopitem1 
loopitem2 <- add class to this one 
loopitem3 
loopitem4 <- add class to this one 
loopitem5 
loopitem6 <- add class to this one 

我怎样才能做到这一点？

我的循环如下所示：

while ($timeline = $fetchtimeline->fetch(PDO::FETCH_ASSOC)) { 

} 

提前感谢！

---

编辑;我现在所拥有的;

  <?php 
      $counter = 0; 

      while ($timeline = $fetchtimeline->fetch(PDO::FETCH_ASSOC)) { 
       $inverted = ""; 
       if($counter == 2) { 
        $inverted = 'class="timeline-inverted"'; 
        $counter = 0; 
       } else { 
        $counter++; 
       } 
       ?> 
    <li <?php echo $inverted; ?>> 
     <div class="timeline-badge primary"><i class="fa fa-hashtag"></i></div> 
     <div class="timeline-panel"> 
     <div class="timeline-heading"> 
      <h4 class="timeline-title"><?php echo $timeline['title']; ?></h4> 
      <p><small class="text-muted"><?php echo $engine->readable($timeline['timestamp']); ?> by <?php echo $engine->pullName($timeline['postedby']); ?></small></p> 
     </div> 
     <div class="timeline-body"> 
      <p><?php echo $timeline['content']; ?></p> 
     </div> 
     </div> 
    </li> 
       <?php 
      } 
      ?> 

Answer 1

正如评论所说，使用the modulo operator。特别为您的示例代码：

$i = 0; 
while ($timeline = $fetchtimeline->fetch(PDO::FETCH_ASSOC)) { 
    $i++; 
    if ($i % 2 === 0) { 
     // add your class here 
    } 
} 

Answer 2

你可以使用一些

<?php 

$array = [1,2,3,4,5,6,7,8,9]; 

foreach ($array as $a) { 
    if ($a % 2 == 0) { 
     echo $a; 
    } 
} 

Answer 3

使用的模量的计数器来跟踪你有多少个循环是，并确保你每一个成功的第二环复位。

$counter = 0; 
while ($timeline = $fetchtimeline->fetch(PDO::FETCH_ASSOC)) { 
    if ($counter == 2) { 
    do_stuff_here 
    $counter = 0; 
    } 
    else { 
    $counter++; 
    } 
}