load more post

// load more post  function.php
add_action('wp_ajax_load_posts_by_ajax', 'load_posts_by_ajax_callback');
add_action('wp_ajax_nopriv_load_posts_by_ajax', 'load_posts_by_ajax_callback');

function load_posts_by_ajax_callback() {
	check_ajax_referer('load_more_posts', 'security');
	$paged = $_POST['page'];	
	$newsletter_lists = get_posts(array('post_type'=>'newsletter','posts_per_page' => 8,'paged' => $paged,)); 
		 	if ( $newsletter_lists ) {
		 	    foreach ( $newsletter_lists as $newsletter_list ) :
		 	    	
		 	        setup_postdata( $newsletter_list ); 
		 	        $thumb_url = get_thumbanil_url($newsletter_list,'full'); ?>
		         <div class="col-md-3"> 
					<div class="news_item">
						<figure>
							<a href="#"><img class="img-fluid" src="<?php echo $thumb_url; ?>" alt=""></a>
							<figcaption>
								<a href="#">
									<h4 class="h4"><?php echo $newsletter_list->post_title; ?></h4>
									<p>Issued on <?php echo get_the_date('M Y',$newsletter_list->ID); ?></p>
								</a>
							</figcaption>
						</figure>
					</div>
					<!-- /.news_item -->
				</div>
				<!-- /.col-md-3 -->   
		         <?php
		 	    endforeach; 
		     wp_reset_postdata();
		 	}
			else{
    		 echo $er = "No more posts to load";
			}

	wp_die();
}

_______________________________
	<div class="row m-t-70">
						 <?php $newsletter_lists = get_posts(array('post_type'=>'newsletter','posts_per_page' => 8)); 
						 $i = 1;
						 	if ( $newsletter_lists ) {
						 	    foreach ( $newsletter_lists as $newsletter_list ) :
						 	    	// print_r(post);
						 	        setup_postdata( $newsletter_list ); 
						 	        $thumb_url = get_thumbanil_url($newsletter_list,'full'); ?>
						         <div class="col-md-3"> 
									<div class="news_item">
										<figure>
											<a href="#"><img class="img-fluid" src="<?php echo $thumb_url; ?>" alt=""></a>
											<figcaption>
												<a href="#">
													<h4 class="h4"><?php 	echo $newsletter_list->post_title; ?> </h4>
													<p>Issued on <?php echo get_the_date('M Y'); ?></p>
												</a>
											</figcaption>
										</figure>
									</div>
									<!-- /.news_item -->
								</div>
								<!-- /.col-md-3 -->   
						         <?php
						         $i++;
						 	    endforeach; 
						     wp_reset_postdata();
						 	}
						 
						  ?>    
						
						    <div class="center">
							 	<!-- <a href="#" class="fps-btn li-pink-btn">see More</a> -->
							 	<div class="loadmore fps-btn li-pink-btn">See More</div>
							 	<div class="loading_more"></div>

							</div>
						
					</div>
					<!-- /.row -->