How to apply "cases" for fixed positioned posts in a loop?

Two approaches to this depending on your browser compatibility requirements.

1) Front-end (CSS)

You can use the :nth-child() declaration to apply styling to the 1, 5, 10… post on the page. You can find a demo/generator (and link to Chris’ in-depth article) here: https://css-tricks.com/examples/nth-child-tester/

This would be my preferred method, but the downside is that IE only supports this from version 9+ – if that matters to you.

2) Back-end (PHP)

The other approach would be to add a class name to the 1, 5, 10… post during the loop. At the top of your loop, increase a variable, and then check it’s value to see if it qualifies for your special class name or not. If it does, you can pass the class name to post_class() in your markup.

To check the value of your counter, you can use something like the modulus operator: https://php.net/manual/en/language.operators.arithmetic.php

Thank you for your suggestion.
I will manage to do with loop because at the specific position, I have the different way to show the post.
The problem is I can’t check the current position of posts in the loop with an interger. I have tried to use Swith/Case function, however, it only show the right layout, but no content at all.
This is some code that I’ve used:

<?php $recent = new WP_Query('posts_per_page=70');
 $i = $wp_query->current_post; // Start from the beginning of the loop
swith ($i){
 case 1: case 6:
 // show the posts here
 break;
 case 5: case 10:
 // show the posts matched here
 break;
 default:
 // show the rest posts here
 break;
}
?>

Now how to check the current_post in loop with integer and what should be used to print the post content?
Thanks.

I finally manage to do it. I forgot to change $wp_query->current_post into $recent->current_post, that’s why my $i always be -1 ??
Thanks