Autoset Featured Image

gistfile1.php

function autoset_featured() {
	global $post;
	
	if ( empty( $post ) ) return;
	
	$already_has_thumb = has_post_thumbnail( $post->ID );
	
	if ( !$already_has_thumb ) {
		$attached_image = get_children( array( 'post_parent' => $post->ID, 'post_type' => 'attachment', 'post_mime_type' => 'image', 'numberposts' => '1' ) );
		if ( $attached_image ) {
			$count = 0;
			foreach ( $attached_image as $attachment_id => $attachment ) {
				set_post_thumbnail( $post->ID, $attachment_id );
				$count++;
			}
		}
	}
}