How to alternate background colour every other div in PHP

Question

I'm currently working on creating a website with a blogging platform, and I want every other post container on the home page to alternate colours. Like light blue, then dark blue, light blue, dark blue, light blue, etc. I'm using a while loop to get 5 posts from the mysql database. Here is my code.

<?php
$sql = mysql_query("SELECT * FROM posts ORDER BY id DESC LIMIT 6");
$array = mysql_fetch_array($sql);
while ($array = mysql_fetch_array($sql)) {

//The php below this is the problem

$counter = 0;
$counter++;

$postcolour =  WHAT DO I PUT HERE ? 'lightblue' : 'darkblue';


?>


<div class="postcontainer" style="background-color: <?php echo $postcolour; ?>;">
</div> <?php } ?>

Answer 1

只需使用模数二：

$postcolour = $counter % 2 ? 'lightblue' : 'darkblue';

Answer 2

I'd just use CSS:

.postcontainer {
    background-color: lightblue;
}

.postcontainer:nth-of-type(even) {
    background-color: darkblue;
}

Here's a demo!