Using Conditional Statement in functions.php

Question

I've got this code below in my functions.php and I'd like to add two filters with conditional statement not to effect every query_posts. Something like this

if(!is_admin() && is_page('Home')){ //two filters }

However, I don't know PHP well enough to know where to put it or how to use the <?php> tags. Can anyone advise? It is from this thread that was closed in WP Forums.

add_filter('posts_orderby', 'edit_posts_orderby');
add_filter('posts_join_paged','edit_posts_join_paged');

function edit_posts_join_paged($join_paged_statement) {
    global $wpdb;
    $join_paged_statement = "LEFT JOIN ".$wpdb->prefix."wpv_voting ON ".$wpdb->prefix."wpv_voting.post_id = $wpdb->posts.ID";
    return $join_paged_statement;
}

function edit_posts_orderby($orderby_statement) {
    global $wpdb;
    $orderby_statement = "(".$wpdb->prefix."wpv_voting.vote_count) DESC";
    return $orderby_statement;
}

Answer 1

Basically, you put the second block into the first. And wait until the last moment:

add_action( 'pre_get_posts', 'wpse_71899_start_filter' );

function wpse_71899_start_filter()
{
    // wrong page
    if ( ! is_page( 'Home' ) )
        return; // stop here.

    add_filter('posts_orderby', 'edit_posts_orderby');
    add_filter('posts_join_paged','edit_posts_join_paged');
}

function edit_posts_join_paged($join_paged_statement) {
    global $wpdb;
    $join_paged_statement = "LEFT JOIN ".$wpdb->prefix."wpv_voting ON ".$wpdb->prefix."wpv_voting.post_id = $wpdb->posts.ID";
    return $join_paged_statement;
}

function edit_posts_orderby($orderby_statement) {
    global $wpdb;
    $orderby_statement = "(".$wpdb->prefix."wpv_voting.vote_count) DESC";
    return $orderby_statement;
}

In your theme’s functions.php should be only one <?php tag: at the first line.

You can place this code anywhere in that file, at the bottom for example.