How to exclude the word "class" from being matched in search?

Question

I would like to exclude the word "class" from being matched to the search term "lass".

On a site I'm helping manage, the search term "lass" is quite prominent. Unfortunately, that matches the common usage of "class" within the content of many, many WP posts, returning plenty of irrelevant results. However, I still want posts with the word "class" in to be possible matches, I just don't want it to match "lass" to "class".

Here are three possible posts:

1.
<a href="http://path/to/image-large.jpg"><img class="aligncenter size-full wp-image-1234" alt="Image" src="http://path/to/image.jpg"" width="600" height="300" /></a>

Lorem ipsum dolor sit amet, consectetur adipisicing elit. Ipsum et veritatis pariatur deleniti excepturi beatae voluptatum aspernatur voluptates rerum numquam.

2.
<a href="http://path/to/image-large.jpg"><img class="aligncenter size-full wp-image-1234" alt="Image" src="http://path/to/image.jpg"" width="600" height="300" /></a>

Lass is lorem ipsum dolor sit amet, consectetur adipisicing elit. Ipsum et veritatis pariatur deleniti excepturi beatae voluptatum aspernatur voluptates rerum numquam.

3.
Lass is lorem ipsum dolor sit amet, consectetur adipisicing elit. Ipsum et veritatis pariatur deleniti excepturi beatae voluptatum aspernatur voluptates rerum numquam.

If I was to search for "lass", I would like results 2 and 3 to be returned, but not result 1.

I've seen the excellent results in these two questions, but they didn't quite meet everything I'm looking for. Any suggestions would be appreciated.

Answer 1

You might try to use the posts_search filter as elegantly suggested by @Kaiser in the first link you provided. Here is one idea:

function filter_search($sql){
    global $wpdb;
    if( strpos(get_query_var("s"),"lass") !== false AND strpos(get_query_var("s"),"class") === false ){
        $sql .= " AND {$wpdb->posts}.post_title NOT LIKE '%class%'";
        $sql .= " AND {$wpdb->posts}.post_content NOT LIKE '%class%'"; 
    }
    return $sql;
}
add_filter( 'posts_search', 'filter_search');

to check if the search term contains lass and not class and then modify the search query to exclude class.

The change in the SQL will look like this:

Before:

AND (((wp_posts.post_title LIKE '%lass%') OR (wp_posts.post_content LIKE '%lass%'))) 

After:

AND (((wp_posts.post_title LIKE '%lass%') OR (wp_posts.post_content LIKE '%lass%'))) 
AND wp_posts.post_title NOT LIKE '%class%' AND wp_posts.post_content NOT LIKE '%class%'

Update:

You can try

   function filter_search($sql){
        global $wpdb;
        if( strpos(get_query_var("s"),"lass") !== false AND strpos(get_query_var("s"),"class") === false ){
            $sql .= " AND ( {$wpdb->posts}.post_content LIKE 'lass %'"; 
            $sql .= " OR {$wpdb->posts}.post_content LIKE '% lass %'"; 
            $sql .= " OR {$wpdb->posts}.post_content LIKE '% lass' )"; 
        }
        return $sql;
    }
    add_filter( 'posts_search', 'filter_search');

if you want to target the exact word lass in the post content.