<?php
/****************************CODE-2**************************************
* @Author: Boutros AbiChedid 
* @Date:   June 6, 2012
* @Websites: bacsoftwareconsulting.com/ ; blueoliveonline.com/
* @Description: Exclude ALL pages and Attachments from WP Search Results.
* Function searches In ALL Posts and Custom Post Types Only.
* @Tested on: WordPress version 3.3.2 
*************************************************************************/
function bac_filter_wp_search($query) { 
	//Filter Search only in the front-end and Not in the Admin.
	if (!$query->is_admin && $query->is_search) {
	//Search in Posts and CPTs only. Excludes Pages and Attachments .
	$query->set('post_type', array('post', 'your-CPT-name-here'));
	}
	return $query;
}
add_filter('pre_get_posts','bac_filter_wp_search');
?>

CODE-2 Notes:

You can use CODE-1 OR CODE-2 but NOT both.

CODE-2 will return results from ALL posts and from Custom Post Type called ´your-CPT-name-here´. You should replace that with your Custom Post Type name.

Line 12 of CODE-2: Also checks not to affect searches in your WordPress dashboard (Admin side). This code will filter only searches done on the front-end of the Blog.

If you have several CPTs that you want to include in your WordPress Search Results along with your Posts. Then, separate them by a comma. For instance if you have 2 CPTs, then replace Line 14 of CODE-2 with the following:

//Search in ALL Posts and 2 CPTs. Separate them by commas.
$query->set('post_type', array('post', 'your-CPT-name-here1', 'your-CPT-name-here2' ));

If you want to exclude a Custom Post Type from search results then add exclude_from_search => true, when you register your post type.

<?php
/****************************CODE-3****************************
* @Author: Boutros AbiChedid 
* @Date:   June 6, 2012
* @Websites: bacsoftwareconsulting.com/ ; blueoliveonline.com/
* @Description: Exclude Certain Pages and Posts by ID. 
* @Tested on: WordPress version 3.3.2 
**************************************************************/
function bac_filter_wp_search($query) { 
	//Filter Search only in the front-end and Not in the Admin.
	if (!$query->is_admin && $query->is_search) {
	//Excludes specific Pages and Posts by ID. Separated by comma.
	$query->set('post__not_in', array(1,1158));
	}
	return $query;
}
add_filter('pre_get_posts','bac_filter_wp_search');
?>

CODE-3 Notes:

Line 11 of CODE-3: Also checks not to affect searches in your WordPress dashboard (Admin side). This code will filter only searches done on the front-end of the Blog. The search in the Back-end is NOT affected.

Line 13 of CODE-3: The number 1 is a page ID on this blog, and the the number 1158 is a post ID on this blog. You need to replace these numbers with yours. If you don´t know how to find the Page ID or Post ID, then read my previous tutorial on How To Find the Page and Post ID.

On line 13 of CODE-3: You can exclude as many pages as you want, just add the IDs to the array separated by commas. You can also use this code to exclude child-pages (or SubPages). You can also exclude posts by ID.

<?php
/****************************CODE-4****************************
* @Author: Boutros AbiChedid 
* @Date:   June 6, 2012
* @Websites: bacsoftwareconsulting.com/ ; blueoliveonline.com/
* @Description: Exclude Certain Categories by ID. 
* @Tested on: WordPress version 3.3.2 
**************************************************************/
function bac_filter_wp_search($query) { 
	//Filter Search only in the front-end and Not in the Admin.
    if (!$query->is_admin && $query->is_search) {
	//Excludes specific Categories by ID. Separate by comma.
	$query->set('cat','-143,-294');
	}
	return $query;
}
add_filter('pre_get_posts','bac_filter_wp_search');
?>

CODE-4 Notes:

Line 11 of CODE-4: Also checks not to affect searches in your WordPress dashboard (Admin side). This code will filter only searches done on the front-end of the Blog. The search in the Back-end is NOT affected.

Line 13 of CODE-4: The numbers 143 and 294 are two category IDs on this blog, you need to replace these number with yours. If you don´t know how to find the Category ID, read my previous tutorial on How To Find the category ID.

Line 13 of CODE-4: the minus sign excludes the specific categories (e.g. -143 exclude all posts having the Category ID of 143). The minus sign is important. If you don´t add it, the search will show ONLY results under category ID of 143.

What will happen if a post is assigned to multiple categories Even if you assign a post under several categories, when one of the categories is excluded from the Search, the post will NOT show in the search results.

<?php
/****************************CODE-5****************************************
* @Author: Boutros AbiChedid 
* @Date:   June 6, 2012
* @Websites: bacsoftwareconsulting.com/ ; blueoliveonline.com/
* @Description: Search in Posts Only BUT Exclude Certain Posts by Category. 
* Also Exclude Pages, Attachments and CPTs.
* @Tested on: WordPress version 3.3.2 
***************************************************************************/
function bac_filter_wp_search($query) { 
	 //Filter Search only in the front-end and Not in the Admin.
     if (!$query->is_admin && $query->is_search) {
	 //Search in Posts only. Excludes Pages, Attachments and CPTs.
     $query->set('post_type','post');
     
     //But Exclude certain Posts belonging to a specific Category ID.
	 $query->set('cat','-143');
	}
	return $query;
}
add_filter('pre_get_posts','bac_filter_wp_search');
?>