问第n个子代的PHP等效项

EN

$posts = array(); //The whatever thing that contains the posts you are concerned about
for ($i = 1; $i<=count($posts); $i++) {
    if($i == /*selector condition*/) {
        //do what you do with the targeted posts
    } else {
        //do what you do with all others
    }
}

function nthChild($multiplier, $addition, $max)
{
    $validInedexes = array();

    for ($n = 0; $n < $max; $n++)
    {
        $idx = $multiplier * $n + $addition;
        if ($idx > $max)
        {
            return $validInedexes;
        }
        $validInedexes[] = ($idx - 1);
    }
}

$query = new WP_Query('...');
$posts = ($count = $query->post_count) ? range(1, $count) : array();
foreach (array_chunk($posts, 3) as $row => $rowIndexes)
{
    foreach ($rowIndexes as $column => $index)
    {
        $query->the_post();
        $middle = $column === 1;
        ...
    }
}