get_posts output always same post

Question

I'm trying to output the last (chronologically) 4 posts having the tag (slug) "pp".

<ul>
<?php
$args = array( 'posts_per_page' => 4, 'taxonomy' => 'tag', 'field' => 'slug', 'terms' => 'pp' );
$tag_posts = get_posts( $args );
foreach ( $tag_posts as $post ) : 
  setup_postdata( $post ); ?>
    <li><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></li>
<?php endforeach; 
wp_reset_postdata(); ?>
</ul>

This snippet though output 4 entries of the same post, which is the fourth from last! How come? :)

Answer 1

This is because you are not passing the parameters in the correct way, taxonomy param needs to be passed under tax_query. Please replace the $args with the below:--

$args = array(
    'posts_per_page' => 4,
    'tax_query' => array(
        array(
            'taxonomy' => 'tag',
            'field' => 'slug',
            'terms' => 'pp'
        )
    )
);

For more details check the codex