Wordpress, display more posts on a subpages

Question

i want to show more posts on my subpages

My code in the functions.php

function number_of_posts($query)
{
    if($query->is_main_query())
    {
       $paged = $query->get( 'paged' );
       if ( ! $paged || $paged < 2 ) 
       {

       } 
       else 
       {
           $query->set('posts_per_page', 24);
       }
    }
    return $query;
}
add_filter('pre_get_posts', 'number_of_posts');

Problem: On the first page i get a wrong pagination. It shows a link to subpage 4 but a subpage 4 doesn't exit.

I think i must add something like this

....
if ( ! $paged || $paged < 2 ) 
{

// show only 10 posts but calculate the pagination with 18 posts

} 
.....

Is this possible?

Answer 1

Here is a modified version of a post I have done on WPSE a while ago

FROM WPSE

STEP 1

We neet to get the posts_per_page option set from the back end (which should be set to 10) and also set your offset which we are going to use. That will be 14 as you will need 24 posts on page one and 24 on the rest.

If you don't want to alter the posts_per_page option, you can then just simply set the variable $ppg to 10

$ppg = get_option( 'posts_per_page' );
//$ppg = 10;
$offset = 14;

STEP 2

On page one, you'll need to subtract the offset to posts_per_page

$query->set( 'posts_per_page', $ppp - $offset );

STEP 3

You must apply your offset to all subsequent pages, otherwise you will get a repetition of the last post of the page on the next page

$offset = ( ( $query->query_vars['paged']-1 ) * $ppp ) - $offset;
$query->set( 'posts_per_page', $ppp );
$query->set( 'offset', $offset ); 

STEP 4

Lastly, you need to add your offset to found_posts otherwise your pagination will will not show the last page

add_filter( 'found_posts', function ( $found_posts, $query ) 
{
    $offset = 14;

    if( $query->is_home() && $query->is_main_query() ) {
        $found_posts = $found_posts + $offset;
    }
    return $found_posts;
}, 10, 2 );

ALL TOGETHER

This is how your complete query will look like that should go into functions.php

add_action('pre_get_posts', function ( $query ) 
{
    if ( !is_admin() && $query->is_main_query() ) {
        $ppp    = get_option( 'posts_per_page' );
        //$ppp  = 10;
        $offset = 14;

        if ( !$query->is_paged() ) {
            $query->set( 'posts_per_page', $ppp - $offset );
        } else {
            $offset = ( ( $query->query_vars['paged']-1 ) * $ppp ) - $offset;
            $query->set( 'posts_per_page', $ppp );
            $query->set( 'offset', $offset );
        }
    }
});

add_filter( 'found_posts', function ( $found_posts, $query ) 
{
    $offset = 14;

    if( $query->is_main_query() ) {
        $found_posts = $found_posts + $offset;
    }
    return $found_posts;
}, 10, 2 );