PHP

get featured image post wordpress by post id

<?php if (has_post_thumbnail( $post->ID ) ): ?>
  <?php $image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'single-post-thumbnail' ); ?>
  <div id="custom-bg" style="background-image: url('<?php echo $image[0]; ?>')">

  </div>
<?php endif; ?>

wordpress featured image show

<?php echo the_post_thumbnail(); ?>

get featured image id wordpress

get_post_thumbnail_id($post) 

wordpress get post featured image

//default 
$image_url = wp_get_attachment_url(1234);
// change if post have feature image
if (has_post_thumbnail($recent_post['ID'])) {
	$image_url = wp_get_attachment_url(get_post_thumbnail_id($recent_post['ID']), '');
}

show featured image in post wordpress

<?php if(has_post_thumbnail()){
  the_post_thumnbail('cstm_name', array( 'class' => 'class1 class2' ))
} else { ?>
  <img class="card-img-top" src="http://placehold.it/750x300" alt="Card image cap" class="img-responsive">
<?php } ?>