Create filter for listpost in admin

filter.php

<?php

/**
 * Summary
 * Description.
 *
 * @since  0.9.0
 * @package
 * @subpackage
 * @author nguyenvanduocit
 */
class ET_Filter {
	private static $instance;

	public static function get_instance() {
		if ( NULL == self::$instance ) {
			self::$instance = new ET_Filter();
		}

		return self::$instance;
	}

	public function init() {
		add_action( 'restrict_manage_posts', array( $this, 'add_filter' ) );
		add_action( 'pre_get_posts', array( $this, 'posts_filter' ) );
	}

	/**
	 * Add filter control.
	 *
	 * @since  0.9.0
	 * @see
	 * @return void
	 * @author nguyenvanduocit
	 */
	public function add_filter() {
		if ( isset( $_GET[ 'post_type' ] ) ) {
			$type = $_GET[ 'post_type' ];
		}
		//only add filter to post type you want
		if ( 'thread' === $type ):
			//change this to the list of values you want to show
			//in 'label' => 'value' format
			$values = array(
				'all'                 => 'Reply filter',
				'wait_customer_reply' => 'Wait for customer',
				'wait_mod_reply'      => 'Wait for mod',
				'not_reply'           => 'not reply'
			);
			?>
			<select name="reply_filter">
				<?php
				$current_v = isset( $_GET[ 'reply_filter' ] ) ? $_GET[ 'reply_filter' ] : '';
				foreach ( $values as $value => $label ):
					printf
					(
						'<option value="%s"%s>%s</option>',
						$value,
						$value == $current_v ? ' selected="selected"' : '',
						$label
					);
				endforeach;
				?>
			</select>
		<?php
		endif;
	}

	public function posts_filter( $query ) {
		global $pagenow;
		$type = 'post';
		if ( isset( $_GET[ 'post_type' ] ) ) {
			$type = $_GET[ 'post_type' ];
		}
		if ( 'thread' === $type && is_admin() && 'edit.php' === $pagenow && isset( $_GET[ 'reply_filter' ] ) && $_GET[ 'reply_filter' ] !== '' ) {
			if ( ! empty( $_GET[ 'post_status' ] ) ) {
				$query->set( 'post_status', $_GET[ 'post_status' ] );
			}
			$filter_key = $_GET[ 'reply_filter' ];
			switch ( $filter_key ) {
				case 'not_reply':
					$meta_query =
						array(
							'relation' => 'AND',
							array(
								'relation' => 'OR',
								array(
									'key'     => 'et_replies_count',
									'compare' => 'NOT EXISTS'
								),
								array(
									'key'     => 'et_replies_count',
									'value'   => 0,
									'compare' => '='
								)
							),
						);
					$query->set( 'meta_query', $meta_query );
					break;
				case 'wait_customer_reply':
					$mod_ids    = et_get_moderator_supporter_id();
					$meta_query = array(
						'relation' => 'AND',
						array(
							'relation' => 'AND',
							array(
								'key'     => 'et_last_author',
								'value'   => $mod_ids,
								'compare' => 'IN'
							)
						)
					);
					$query->set( 'meta_query', $meta_query );
					$query->set( 'author__not_in', $mod_ids );
					break;
				case 'wait_mod_reply':
					$mod_ids    = et_get_moderator_supporter_id();
					$meta_query = array(
						'relation' => 'OR',
						array(
							'key'     => 'et_last_author',
							'value'   => $mod_ids,
							'compare' => 'NOT IN'
						),
						array(
							'key'     => 'et_last_author',
							'compare' => 'NOT EXISTS'
						),
					);
					$query->set( 'meta_query', $meta_query );
					$query->set( 'author__not_in', $mod_ids );
					break;
			}
		}

		return $query;
	}
}