Exclude the category from the WordPress loop

Question

I have this code for the loop, and I need to exclude a category 4 from this loop. Any suggestions on how to achieve this?

Code that starts the loop

 <?php if(have_posts()): ?>

    <ol class="item_lists">

        <?php
        $end = array(3,6,9,12,15,18,21,24,27,30,33,36,39,42,45);
        $i = 0;

        while (have_posts()) : the_post();
           $i++;
           global $post;
 ?>

Answer 1

you could use wp_parse_args() to merge your arguments into the default query

// Define the default query args
global $wp_query;
$defaults = $wp_query->query_vars;

// Your custom args
$args = array('cat'=>-4);

// merge the default with your custom args
$args = wp_parse_args( $args, $defaults );

// query posts based on merged arguments
query_posts($args);

although, i think the more elegant route is using the pre_get_posts() action. this modifies the query before the query is made so that the query isn't run twice.

check out:

http://codex.wordpress.org/Custom_Queries#Category_Exclusion

based on that example to exclude category 4 from the index i'd put this in your functions.php:

add_action('pre_get_posts', 'wpa_44672' );

function wpa_44672( $wp_query ) {

    //$wp_query is passed by reference.  we don't need to return anything. whatever changes made inside this function will automatically effect the global variable

    $excluded = array(4);  //made it an array in case you  need to exclude more than one

    // only exclude on the home page
    if( is_home() ) {
        set_query_var('category__not_in', $excluded);
        //which is merely the more elegant way to write:
        //$wp_query->set('category__not_in', $excluded);
    }
}

Answer 2

From your functions file

function remove_home_category( $query ) {
    if ( $query->is_home() && $query->is_main_query() ) {
        $query->set( 'cat', '-4' );
    }
}
add_action( 'pre_get_posts', 'remove_home_category' );

This code alters the query before the actual query is run so is the most efficient hook to modify the loop in this case.

Answer 3

Before the line

<?php if(have_posts()): ?>

Insert something like this

<?php query_posts($query_string . '&cat=-4'); ?>

This excludes the category with Category ID 4. As seen here

Answer 4

Adam is right. In addition, for pagination to work, you need to have something more like so:

<?php query_posts('post_type=post&paged='.$paged.'&cat=-4');  ?>