<div class="search-cont">
        <form class="searchinput" method="get" action="<?php echo home_url(); ?>" role="search">
        <input type="search" class="searchinput" placeholder="<?php echo esc_attr_x( 'Click icon or hit enter to search..', 'placeholder' ) ?>" value="<?php get_search_query() ?>" name="s" title="<?php echo esc_attr_x( 'Search for:', 'label' ) ?>" />
        <button type="submit" role="button" class="search-btn"/><i class="fa fa-search" aria-hidden="true"></i></button>
        </form>
        </div>

<div class="searchresultsbox">
                  <?php global $wp_query;?>
      <h2> <?php echo $wp_query->found_posts; ?><?php _e( ' results found for', 'locale' ); ?>: "<?php the_search_query(); ?>"</h2>
                <?php if ( have_posts() ) { ?>
            <h3><?php printf( __( 'Your "%s" search results can be found at:', 'ptpisblogging' ), get_search_query() ); ?></h3>
            <?php while ( have_posts() ) { the_post(); ?>
                 <h3><a href="<?php echo get_permalink(); ?>">
                   <?php the_title();  ?>
                 </a></h3>
                 <?php //echo substr(get_the_excerpt(), 0, 2); ?>
                 <div class="h-readmore"> <a href="<?php //the_permalink(); ?>"></a></div>
               <?php
 $args=array('s'=>'test','order'=> 'DESC', 'posts_per_page'=>get_option('posts_per_page'));
   $query=new WP_Query($args);
  if( $query->have_posts()):
  while( $query->have_posts()): $query->the_post();
 {
   echo $post->post_title;
   echo $post->post_content;
 }
 endwhile;
 else:
 endif;
 ?>
 <?php } ?>
 <?php paginate_links(); ?>
        <?php } ?>
    </div>
  </div>
</div>
<param name="" value="">
                </div><!-- /searchresultsbox -->
            </div><!-- /collcelltwo -->
        </div><!-- /tb-one-row -->
    </div><!-- /tb-one -->

add_action( 'pre_get_posts', function( $query ) {
        // Check that it is the query we want to change: front-end search query
        if( $query->is_main_query() && ! is_admin() && $query->is_search() ) {
        // Change the query parameters
        $query->set( 'posts_per_page', 4 );
        }
        } );

// $searchresult = result of search process,
//$highlightword = word you want to highlight
$searchresult = str_replace($highlightword,
     "<span style="background-color:#ffff00;">$highlightword</span>",
      $searchresult);