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<?php
/* 投稿一覧にスラッグを表示する */
function add_posts_columns_slug($columns) {
    $columns['slug'] = 'スラッグ';
    return $columns;
}
function add_posts_columns_slug_row($column_name, $post_id) {
    if( 'slug' == $column_name ) {
        $slug = get_post($post_id) -> post_name;
        echo $slug;
    }
}
add_filter( 'manage_posts_columns', 'add_posts_columns_slug' );
add_action( 'manage_posts_custom_column', 'add_posts_columns_slug_row', 10, 2 );
/* 固定ページにスラッグを表示する */
function add_page_columns_name($columns) {
	$columns['slug'] = "スラッグ";
	return $columns;
}
function add_page_column($column_name, $post_id) {
	if( $column_name == 'slug' ) {
		$post = get_post($post_id);
		$slug = $post->post_name;
		echo esc_attr($slug);
	}
}
add_filter( 'manage_pages_columns', 'add_page_columns_name');
add_action( 'manage_pages_custom_column', 'add_page_column', 10, 2);
function disable_visual_editor_in_page(){
    global $typenow;
    if( $typenow == 'page' ){
        add_filter('user_can_richedit', 'disable_visual_editor_filter');
    }
}
function disable_visual_editor_filter(){
    return false;
}
add_action( 'load-post.php', 'disable_visual_editor_in_page' );
add_action( 'load-post-new.php', 'disable_visual_editor_in_page' );