Filter WP post_category Array in get_posts() loop.

loop.php

<?php
$posts = get_posts();
foreach( $posts as $post ):
	
	// filter post_category array
	if( is_array($post->post_category) )
		foreach( $post->post_category as $k => $v )
			$post->post_category = $v;

endforeach;
?>