set_current_screen() 前に管理画面のポストタイプだったりを取得するクラス

after_setup_theme だったり init など、$GLOBALS['typenow']、$GLOBALS['taxnow'] が定義されていない段階で取得する。

code

<?php

class WPQuickScreen {

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

    /**
     * @var null|string
     */
    private $typenow;

    /**
     * @var null|string
     */
    private $taxnow;

    private static $query_filter_diffinitions = array(
        'action'    => \FILTER_SANITIZE_ENCODED,
        'post_type' => \FILTER_SANITIZE_ENCODED,
        'taxonomy'  => \FILTER_SANITIZE_ENCODED,
        'post'      => \FILTER_VALIDATE_INT,
        // and more
    );

    public static function getInstance() {
        static $instance;
        return $instance ?: $instance = new self();
    }

    public function __get( $name ) {
        return property_exists( $this, $name ) ? $this->$name : null;
    }

    private function __construct() {
        if ( ! is_admin() ) {
            return;
        }
        global $pagenow;
        $this->pagenow = $pagenow;
        $this->parse_query();
    }

    private function parse_query() {
        $q = filter_input_array( INPUT_GET, self::$query_filter_diffinitions );
        switch ( $this->pagenow ) {
            case 'edit.php' :
            case 'post-new.php' :
                $this->typenow = $q['post_type'] ?: 'post';
                break;
            case 'post.php' :
                /**
                 * @see https://ja.forums.wordpress.org/topic/150122
                 */
                $this->typenow = $q['post'] ? get_post_type( $q['post'] ) : filter_input( \INPUT_POST, 'post_type' );
                break;
            case 'edit-tags.php' :
            case 'term.php' :
                $this->taxnow = $q['taxonomy'] ?: 'post_tag';
                break;
            case 'index.php' :
                // var_dump( 'Dashboard!!!!!' );
                break;
        }
    }

}

usage

function.php

<?php
add_action( 'after_setup_theme', function() {
    if ( !is_admin() ) {
        return;
    }
    global $pagenow;
    var_dump( $typenow ); // null

    $qscreen = WPQuickScreen::getInstance();
    var_dump( $qscreen->typenow );
} );