WordPressの投稿一覧にカスタムフィールドを表示する。並び替えにも対応。

Admin_Column_Custom_Field.php

<?php

Class Admin_Column_Custom_Field {

	/** @var string  */
	private $field_key;

	/** @var string  */
	private $field_label;

	/** @var string  */
	private $post_type;

	/** @var bool  */
	private $is_num;


	/**
	 * @param string $post_type
	 * @param string $field_key
	 * @param string $field_label
	 * @param bool $is_num
	 */
	public function __construct( $post_type, $field_key, $field_label = '' , $is_num = false ) {

		$this->post_type = $post_type;
		$this->field_key = $field_key;
		$this->field_label = $field_label;

		if ( ! $field_label ) {
			$this->field_label = $field_key;
		}

		$this->is_num = $is_num;

		$this->add_hooks();
	}


	/**
	 *
	 */
	protected function add_hooks() {

		add_filter( 'manage_posts_columns', [ $this, 'manage_posts_columns' ] );
		add_filter( 'manage_edit-' . $this->post_type . '_sortable_columns', [ $this, 'sortable_columns' ] );
		add_action( 'manage_posts_custom_column', [ $this, 'manage_posts_custom_column' ] );
		add_action( 'load-edit.php', function(){
			add_filter( 'request', [ $this, 'sort_edit' ] );
		} );
	}

	/**
	 * @param callable $callback
	 *
	 * @param int $priority
	 */
	public function add_filter( callable $callback , $priority = 10 ) {
		add_filter( 'admin_custom_column_'.$this->post_type.'_'.$this->field_key, $callback, $priority );
	}


	/**
	 * @param array $columns
	 *
	 * @return array
	 */
	public function manage_posts_columns( $columns ) {

		global $post;

		if ( $post->post_type == $this->post_type ) {
			$date = $columns['date'];
			unset( $columns['date'] );
			$columns[ $this->field_key ] = $this->field_label;
			$columns['date']             = $date;
		}

		return $columns;
	}

	/**
	 * @param string $column_name
	 */
	public function manage_posts_custom_column( $column_name ) {
		global $post;

		if ( $post->post_type == $this->post_type ) {

			if ( $column_name == $this->field_key ) {
				$column = get_post_meta( $post->ID, $this->field_key, true );
				$column = apply_filters( 'admin_custom_column_'.$this->post_type.'_'.$this->field_key, $column );
				echo esc_html( $column );
			}

		}

	}

	/**
	 * @param array $columns
	 *
	 * @return array
	 */
	public function sortable_columns( $columns ) {
		$columns[ $this->field_key ] = $this->field_key;

		return $columns;
	}


	/**
	 * @param array $vars $wp_query->query_vars.
	 *
	 * @return array
	 */
	public function sort_edit( $vars ) {
		if ( isset( $vars['post_type'] ) && $this->post_type == $vars['post_type'] ) {

			if ( isset( $vars['orderby'] ) && $vars['orderby'] == $this->field_key ) {

				$vars = array_merge(
					$vars,
					[
						'meta_key' => $this->field_key,
						'orderby'  => ( $this->is_num ) ? 'meta_value_num' : 'meta_value',
					]
				);
			}
		}

		return $vars;

	}
}

usage.php

<?php

$cf_column = new Admin_Column_Custom_Field( 'my_post_type', 'field_key', 'field_label' );

//出力時の値を変更するフィルターを登録。
$cf_column->add_filter('capital_P_dangit');

//こっちでもフィルターできます。動作は全く一緒。
add_filter( 'admin_custom_column_my_post_type_field_key', 'capital_P_dangit' );


$cf_column->add_filter('my_filter');

function my_filter( $value ) {
    return strip_tags( $value );
}