wp_query search not taking keywords with together for multiple words

WordPress also provide more filter to can change wp query using filters. What i need logical to use filter to override query below sample of code if this helpful for you.

add_filter( 'posts_where', 'posts_where_condition_search' );
 $wp_query = new WP_Query( 
        array( 
            'post_type' => 'press-release',
            'posts_per_page' => -1,
        ) 
    );  
 remove_filter( 'posts_where', 'posts_where_condition_search' );    

 function posts_where_condition_search( $where ){

    $search_string = 'test';

    if( isset( $_POST['search']) && !empty($_POST['search']) )
    $search_string = $_POST['search'];

    if( empty($search_string) )
    return $where;
    // add your multiple condition here and write your custom filter

    $where .= " AND (((wp_posts.post_title LIKE '%$search_string%') OR (wp_posts.post_content LIKE '%$search_string%'))) ";
    //$where .= " AND (((wp_posts.post_title LIKE '%$search_string%') OR (wp_posts.post_content LIKE '%$search_string%'))) ";
    //$where .= " AND (((wp_posts.post_title LIKE '%$search_string%') OR (wp_posts.post_content LIKE '%$search_string%'))) ";

   return $where;
}

https://codex.wordpress.org/Class_Reference/WP_Query#Filters