<p>I would like to change the number of posts displayed on certain pages on my WordPress site. </p> <p>I found the following code snippet here: </p> <pre class="brush:php;toolbar:false;">$postsPage = $settings["postspage"]; query_posts('posts_per_page='.$postsPage);</pre> <p>Call before <code>if (have_posts()) while (have_posts()) the_post()</code></p> <p>I'm very new to php, but what I'm trying is this</p> <pre class="brush:php;toolbar:false;">... if ( is_front_page()) { $postsPage = $settings["postspage"] 1; }elseif ( is_tag()) { $postsPage = $settings["postspage"] - 2; } else { $postsPage = $settings["postspage"]; } query_posts('posts_per_page='.$postsPage); ...</pre> <p>But unfortunately it doesn't work. Instead, it only returns 1 post from the homepage instead of 1 of 5 set in the WP menu. I can hardcode the desired value like $postPage = 6; </code> for is_front_page and it works fine. For some reason I can't add/subtract anything from the value given by <code>$settings["postspage"]</code>. It also works if I don't change the value (else-clause). What did I miss? </p> <p>I've tried converting the value of <code>$settings["postspage"]</code> to an integer because I thought it might be returned as a string. I use: <code>$postsPage = (int)$settings["postspage"] 1;</code> or <code>$postsPage = intval($settings["postspage"]) 1;</ code>But without success. Since I'm not very familiar with wordpress functions and their variables, I was looking for the reason why I can't modify the number of posts. I'd appreciate any tips! </p>

add_action( 'pre_get_posts', 'alter_number_of_posts' );

function alter_number_of_posts( $query ) {

    if ( !$query->is_main_query() ){
        return;
    }

    $posts_per_page = get_option( 'posts_per_page' );

    if ( is_front_page() ) {
        $query->set( 'posts_per_page', $posts_per_page + 1 );
        return;
    }
    if ( is_tag() ) {
        $query->set( 'posts_per_page', $posts_per_page - 2 );
        return;
    }
}