Polylang: Display a country flag or the name of the language as a "post state" in post lists

polylang-display-post-states-language.php

<?php
/**
 * Polylang: Display a country flag or the name of the language as a "post state"
 *
 * @param array    $post_states An array of post display states.
 * @param \WP_Post $post        The current post object.
 *
 * @return array A filtered array of post display states.
 */
function polylang_display_post_states_language( $post_states, $post ) {
	if( is_plugin_active( 'polylang/polylang.php' ) ){
		foreach(get_the_terms( $post, 'language' ) as $language){
			if(file_exists(POLYLANG_DIR . '/flags/' . $language->slug . '.png')){
				$post_states['polylang'] = '<img src="data:image/png;base64,' . base64_encode( file_get_contents( POLYLANG_DIR . '/flags/' . $language->slug . '.png' ) ).'">';
			}
			else{
				$post_states['polylang'] = $language->name;
			}
		}
	}
	return $post_states;
}
add_filter( 'display_post_states', 'polylang_display_post_states_language', 10, 2 );