[polylang] create a shortcode to get the 3 last post, of all available languages

functions.php

function jba_register_shortcode() {
	add_shortcode( 'jba_posts', 'jba_shortcode_cb' );
}
add_action( 'init', 'jba_register_shortcode' );

function jba_shortcode_cb( $args ) {
	$args = array(
		'post_type' => 'post',
		'posts_per_page' => 3,
		'tax_query' => '',
		'lang' => '',
	);
	$last_posts = new WP_Query( $args );

	$out = '';
	if ( $last_posts->have_posts() ) {
	    $out .= '<ul>';
		while ( $last_posts->have_posts() ) {
			$last_posts->the_post();
			$out .= sprintf( 
            	'<li><a href="%s">%s</a></li>',
				get_permalink(),
				get_the_title()
			);
		}
		$out .= '</ul>';
	}
    return $out;
}