how to set featured image as background wordpress

Syntax

Use the following to get image
    <?php if (has_post_thumbnail( $post->ID ) ): ?>
<?php $image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'single-post-thumbnail' ); ?>
<?php endif; ?>

 

CSS Code

Use this CSS code to add background image. 

<style type="text/css">style=background-image: url('<?php echo $image[0]; ?>')</style>