Add Featured Image column to Posts admin page - Easily see whether a post has a featured image set. https://www.damiencarbery.com/2022/11/add-featured-image-column-to-posts-admin-page/

posts-featured-image-column.php

<?php
/*
Plugin Name: Add Featured Image column to Posts admin page
Plugin URI: https://www.damiencarbery.com/2022/11/add-featured-image-column-to-posts-admin-page/
Description: Easily see whether a post has a featured image set.
Author: Damien Carbery
Version: 0.1
*/


class AddFeaturedImageColumn {
	// Column key and title.
	private $column_key;
	private $column_title;
	// Name of column to add the new column after.
	private $insert_after;


	// Returns an instance of this class. 
	public static function get_instance() {
		if ( null == self::$instance ) {
			self::$instance = new self;
		} 
		return self::$instance;
	}


	// Initialize the plugin variables.
	public function __construct() {
		$this->column_key = 'featured_image';
		$this->column_title = 'Featured <br/>image';
		// Comment this line out to add column to the end.
		$this->insert_after = 'tags';

		$this->init();
	}


	// Set up WordPress specfic actions.
	public function init() {
		// Add the new column. Could also use 'manage_post_posts_columns'
		add_filter( 'manage_posts_columns', array( $this, 'set_custom_column' ), 20 );
		// Populate the new column with the featured image status. Could also use 'manage_post_posts_custom_column'
		add_action( 'manage_posts_custom_column' , array( $this, 'populate_custom_column' ), 10, 2 );
		// Add CSS to ensure new column width is not distored.
		add_action( 'admin_head', array( $this, 'add_column_css' ) );
	}


	// Add the new column.
	public function set_custom_column( $columns ) {
		// If $this->insert_after is set, and found, add the new column after it.
		if ( isset( $this->insert_after ) ) {
			$position = array_search( $this->insert_after, array_keys( $columns ) );
			if ( false !== $position ) {
				$before = $columns;
				$after = $columns;
				array_splice( $before, $position + 1 );
				array_splice( $after, 0, $position + 1 );
				$before[ $this->column_key ] = $this->column_title; // To avoid wrapping. Add space for 'Screen Options' panel.
				$columns = array_merge( $before, $after );
			}
		}
		else {
			// Otherwise add the new column at the end.
			$columns[ $this->column_key ] = $this->column_title;
			
		}
		
		return $columns;
	}


	// Populate the new column with the featured image status.
	public function populate_custom_column( $column, $post_id ) {
		// Use switch() to  allow for additional columns in the future.
		switch ( $column ) {
			case 'featured_image':
				if ( has_post_thumbnail( $post_id ) ) {
					echo '<span class="dashicons dashicons-yes"></span>';
				}
				else {
					echo '<span aria-hidden="true">&#8212;</span><span class="screen-reader-text">No featured image</span>';
				}
				break;
		}
	}


	// Add CSS to ensure new column width is not distored.
	public function add_column_css() {
		$currentScreen = get_current_screen();
		if ( isset( $currentScreen ) ) {
			//error_log( 'get_current_screen: ' . var_export( $currentScreen, true ) );
			if ( 'edit-post' == $currentScreen->id ) {
?>
<style>table.wp-list-table .column-featured_image { width: 15%; }</style>
<?php
			}
		}
	}
}
$AddFeaturedImageColumn = new AddFeaturedImageColumn();