Class for custom post status in WordPress

class-custom-status.php

<?php
/**
 * Class for custom post statuses
 */
class Custom_Status
{
  protected $status, $labels, $post_type;

  /**
   * Set variables
   * @param string $status
   * @param array $labels
   * @param string $post_type
   */
  public function __construct($status, $labels, $post_type) {
    $this->status = $status;
    $this->labels = $labels;
    $this->post_type = $post_type;
  }

  /**
   * Install custom status
   */
  public function install() {
    add_action( 'init', [$this, 'registerPostStatus'], 1 );
    add_action( 'admin_footer-edit.php', [$this, 'registerOverviewStatusSelect'], PHP_INT_MAX );
    add_filter( 'display_post_states', [$this,'displayOverviewStatus'] );
    add_action( 'admin_footer', [$this, 'displayEditStatus'], PHP_INT_MAX );
  }

  /**
   * Register custom post states
   */
  public function registerPostStatus() {
    $args = [
      'public' => true,
      'show_in_admin_all_list' => true,
      'show_in_admin_status_list' => true,
      'exclude_from_search' => false,
      'label' => $this->labels['name'],
      'label_count' => $this->labels['counter'],
    ];

    register_post_status( $this->status, $args );
  }

  /**
   * Register custom status into the post edit overview
   */
  public function registerOverviewStatusSelect() {
    ?> 
<script id="status-<?=$this->status?>" type="text/javascript">
(function($) { 
  $("select[name=\"_status\"]").append( "<option value=\"<?=$this->status?>\"><?=$this->labels['name']?></option>" ); 
})(jQuery);
</script><?php
  }

  /**
   * Display custom states into the post edit overview
   * @param array $wp_states default wordpress states
   */
  public function displayOverviewStatus($wp_statuses) {    
    if( $this->status !== get_query_var('post_status') ) {
      if( $this->status == $post->post_status ) {
        return [ $this->labels['name'] ];
      }
    }
  	return $wp_statuses;
  }

  /**
   * Display custom states into post edit screen (single)
   */
  public function displayEditStatus() {
    global $post;

    if( $this->post_type !== $post->post_type ) 
      return;

    $html  = '<script>(function($) {';
    $html .= '$(function() { $("#post-status-display").text("'.$this->labels['name'].'"); });';

    if( $this->status == $post->post_status) {
      $html .= '$("#post_status").append("<option value=\"'.$this->status.'\" selected>'.$this->labels['name'].'</option>");';
      $html .= '$(".misc-pub-section.misc-pub-post-status").find("label").append("<span id=\"post-status-display\"> '.$this->labels['name'].'</span>");';
    } else {
      $html .= '$("#post_status").append("<option value=\"'.$this->status.'\">'.$this->labels['name'].'</option>");';
    }

    $html .= '})(jQuery)</script>';
    echo $html;
  }
}

usage.php

<?php
include_once('class-custom-status.php');

$post_status = 'closed';
$post_type = 'my_cpt';

$labels = [
  'name' => esc_html_x( 'Closed', 'Status General Name', 'textdomain' ),
  'counter' => _n_noop( 'Closed (%s)',  'Closed (%s)', 'textdomain' ),
];

$status = new Custom_Status($post_status, $labels, $post_type);
$status->install();