Add a custom post status for WP (custom) post types

example_post_status.php

<?php
// No, Thanks. Direct file access forbidden.
! defined( 'ABSPATH' ) AND exit;

// INIT
add_action( 'after_setup_theme', array( 'unavailable_post_status', 'init' ) );

class unavailable_post_status extends wp_custom_post_status
{
	/**
	 * @access protected
	 * @var string
	 */
	static protected $instance;


	/**
	 * Creates a new instance. Called on 'after_setup_theme'.
	 * May be used to access class methods from outside.
	 *
	 * @return void
	 */
	static public function init()
	{
		null === self :: $instance and self :: $instance = new self;
		return self :: $instance;
	}


	public function __construct()
	{
		// Set your data here. Only "$post_status" is required.
		$this->post_status = 'unavailable';

		// The post types where you want to add the custom status. Allowed are string and array
		$this->post_type = 'post';

		// @see parent class: defaults inside add_post_status()
		$this->args = array();

		parent :: __construct();
	}
}

wp_custom_post_status.php

<?php
// No, Thanks. Direct file access forbidden.
! defined( 'ABSPATH' ) AND exit;
/*
Plugin Name: Custom Post Status
Plugin URI:  http://
Description: Adds a custom post status for posts, pages or custom post types
Author:      Franz Josef Kaiser
Version:     2012-06-14.1426
Author URI:  http://unserkaiser.com/
License:     MIT
 */



class wp_custom_post_status
{
	/**
	 * Name of the post status
	 * Must be lower case
	 * 
	 * @access protected
	 * @var string
	 */
	public $post_status;


	/**
	 * Post type (slug) where the post status should appear
	 * 
	 * @access protected
	 * @var string/array
	 */
	public $post_type = array( 'post', 'page' );


	/**
	 * Custom Args for the post status
	 * 
	 * @access protected
	 * @var string
	 */
	public $args;


	/**
	 * Construct
	 * @return void
	 */
	public function __construct()
	{
		#echo '<pre>'; print_r( $this ); echo '</pre>';
		// We need to have at least a post status name
		if ( ! isset( $this->post_status ) )
			return;

		add_action( 'init', array( $this, 'add_post_status' ), 0 );

		foreach ( array( 'post', 'post-new' ) as $hook )
			add_action( "admin_footer-{$hook}.php", array( $this,'extend_submitdiv_post_status' ) );
	}


	/**
	 * Add a new post status of "Unavailable"
	 * 
	 * @return void
	 */
	public function add_post_status()
	{
		global $wp_post_statuses;

		$defaults = array(
			 'label_count'               => false
			// defaults to FALSE
			,'hierarchical'              => false
			// defaults to FALSE
			,'public'                    => true
			// If NULL, then inherits "public"
			,'publicly_queryable'        => null

			// most important switch
			,'internal'                  => false
			// If NULL, inherits from "internal"
			,'exclude_from_search'       => null
			// If NULL, inherits from "internal"
			,'show_in_admin_all_list'    => null
			// If NULL, inherits from "internal"
			,'show_in_admin_status_list' => null

			// If NULL, will be set to FALSE
			,'protected'                 => null
			// If NULL, will be set to FALSE
			,'private'                   => null
			// not set by the core function - defaults to NULL
			,'show_in_admin_all'         => null
			// defaults to "post"
			,'capability_type'           => 'post'
			,'single_view_cap'           => null 
			// @internal use only - don't touch
			,'_builtin'                  => false
			,'_edit_link'                => 'post.php?post=%d'
		);

		// if FALSE, will take the 1st fn arg
		$defaults['label'] = __( 
		 	 ucwords( str_replace( 
		 	 	 array( '_', '-' )
				,array( ' ', ' ' )
		 	 	,$this->post_status
			 ) )
		 	,'cps_textdomain' 
		 );

		// Care about counters:
		// If FALSE, will be set to array( $args->label, $args->label ), which is not desired
		$defaults['label_count'] = _n_noop( 
			 "{$defaults['label']} <span class='count'>(%s)</span>"
			,"{$defaults['label']} <span class='count'>(%s)</span>"
			,'cps_textdomain'
		);

		// Register the status: Merge Args with defaults
		register_post_status( 
			 $this->post_status
			,wp_parse_args( 
				 $this->args
				,$defaults 
			 )
		);
	}


	/**
	 * Adds post status to the "submitdiv" Meta Box and post type WP List Table screens
	 * 
	 * @return void
	 */
	public function extend_submitdiv_post_status()
	{
		// Abort if we're on the wrong post type, but only if we got a restriction
		if ( isset( $this->post_type ) )
		{
			global $post_type;
			if ( is_array( $this->post_type ) )
			{
				if ( in_array( $post_type, $this->post_type ) )
					return;
			}
			elseif ( $this->post_type !== $post_type )
			{
				return;
			}
		}

		// Our post status and post type objects
		global $wp_post_statuses, $post;

		// Get all non-builtin post status and add them as <option>
		$options = $display = '';
		foreach ( $wp_post_statuses as $status )
		{
			if ( ! $status->_builtin )
			{
				// Match against the current posts status
				$selected = selected( $post->post_status, $status->name, false );

				// If we one of our custom post status is selected, remember it
				$selected AND $display = $status->label;

				// Build the options
				$options .= "<option{$selected} value='{$status->name}'>{$status->label}</option>";
			}
		}
		?>
		<script type="text/javascript">
			jQuery( document ).ready( function($) 
			{
				<?php
				// Add the selected post status label to the "Status: [Name] (Edit)" 
				if ( ! empty( $display ) ) : 
				?>
					$( '#post-status-display' ).html( '<?php echo $display; ?>' )
				<?php 
				endif; 

				// Add the options to the <select> element
				?>
				$( '.edit-post-status' ).on( 'click', function()
				{
					var select = $( '#post-status-select' ).find( 'select' );
					$( select ).append( "<?php echo $options; ?>" );
				} );
			} );
		</script>
		<?php
	}
}

The jQuery should only be called once otherwise, multiple copies are produced. Further, all added post status are added, than only those by this method.

I'll link to my fixes tomorrow when not so groggy.

Changes made at https://github.com/michael-cannon/aihrus-framework/blob/1.1.0RC2/includes/libraries/wp_custom_post_status.php. If the link breaks, change branch to master or 1.1.0 in url.

Also, it should be noted…

• Doesn't affect quick and bulk edit screens
• Doesn't include baseline defaults

I'll worry about these later.

147-148th line
if ( in_array( $post_type, $this->post_type ) ) return;

should be !in_array