WP posts_per_page or showposts? - php

Question

New to PHP. Below is the code to show posts and pagination. I'm trying to get 10 posts per page to show and am confused on what code to write to do this. I tried changing Reading Settings to 10 blog posts, but when I save it, it overwrites back to one. So I figured the setting is being overwritten in php somewhere. I'm looking to overwrite that here. Please help.
I tried adding:
but not only does 10 posts show, so does a second category list below the posts.
<?php get_template_part('templates/page', 'header'); ?>
<?php if (!have_posts()) : ?>
<div class="alert">
<?php _e('Sorry, no results were found.', 'roots'); ?>
</div>
<?php get_search_form(); ?>
<?php endif; ?>
<?php $i = 0; ?>
<?php while (have_posts()) : the_post(); $i++; ?>
<article class="<?php $allClasses = get_post_class(); foreach ($allClasses as $class) { echo $class . " "; } if($i&1) { echo 'odd';} else {echo 'even';}; ?> block clearfix">
<?php get_template_part('templates/content-category', get_post_format()); ?>
</article>
<?php endwhile; ?>
<?php if ($wp_query->max_num_pages > 1) : ?>
<nav class="post-nav">
<ul class="pager">
<li class="previous"><?php next_posts_link(__('← Older posts', 'roots')); ?></li>
<li class="next"><?php previous_posts_link(__('Newer posts →', 'roots')); ?></li>
</ul>
</nav>
<?php endif; ?>

Answer 1

try adding this to your functions.php
function trance_posts_per_page( $query ) {
if (! is_main_query())
return;
$query->set( 'posts_per_page', 20 );
}
add_action( 'pre_get_posts', 'trance_posts_per_page' );
check the plugin WP-PageNavi if this doesn't help you

Answer 2

Got to work by removing this:
<?php $i = 0; ?>
<?php while (have_posts()) : the_post(); $i++; ?>
<article class="<?php $allClasses = get_post_class(); foreach ($allClasses as $class) { echo $class . " "; } if($i&1) { echo 'odd';} else {echo 'even';}; ?> block clearfix">
<?php get_template_part('templates/content-category', get_post_format()); ?>
</article>
<?php endwhile; ?>
and replacing it with this:
<?php query_posts( $query_string . '&posts_per_page=-10' );?>
<?php while (have_posts()) : the_post(); ?>
<article class="block clearfix">
<?php get_template_part('templates/contentcategory',
get_post_format()); ?>
</article>
<br />
<?php endwhile; ?>