WordPress: Add admin columns for a custom post type

wordpress-add-columns-to-post-list--functions.php

<?php

/**
 * CPT: Custom columns for post_slug
 * replace all occurances of "post_slug" with your post type's slug and "theme_domain" with your theme's domain
 */
function set_custom_edit_post_slug_columns( $columns ) {
	// unset( $columns['date'] ); // disable existing column
	$columns['image'] = __( 'Image', 'theme_domain' );
	$columns['date']  = __( 'Custom Date', 'theme_domain' );
	return $columns;
}
add_filter( 'manage_post_slug_posts_columns', __NAMESPACE__ . '\\set_custom_edit_post_slug_columns' );

function custom_post_slug_column( $column, $post_id ) {
	switch( $column ) {
		case 'image':
			$image_url = get_field( 'slide_image_1' );
			if ( $image_url ) {
				echo '<img src="' . $image_url . '" style="width:200px; height:auto;">';
			}
			break;
		case 'date':
			$datetime = get_field( 'slide_starts', $post_id );
			if ( $datetime ) {
				echo date( 'm/d/Y g:i:s a', $datetime );
			} else {
				echo '-';
			}
			break;
	}
}
add_action( 'manage_post_slug_posts_custom_column', __NAMESPACE__.'\\custom_post_slug_column', 10, 2 );