/*
 *Only Search Posts
 */
function SearchFilter($query) {
    if ($query->is_search) {
        $query->set('post_type', 'post');
    }
    return $query;
}

add_filter('pre_get_posts','SearchFilter');

To exclude pages from wordpress search results include the following in your theme's functions.php

Only search WP posts

search, wordpress

PHP