色々なところを参考に作成したのでメモ書き

function.php

	/**
	 * パンくず生成
	 *
	 * @param array $bread_crumns_list パンくずリスト
	 *     key => display_name 表示名
	 *     val => link 遷移先
	 */
	public function bread_crumns($bread_crumns_list) {
	    $item_position_num = 1;
	    $bread_crumns = "<ol itemscope='itemscope' itemtype='http://schema.org/BreadcrumbList'>\n";
	    foreach ($bread_crumns_list as $display_name => $link) {
	        $bread_crumns .= "<li itemprop='itemListElement' itemscope='itemscope' itemtype='http://schema.org/ListItem'>\n";
	        $bread_crumns .= "<a itemprop='item' href='{$link}'>";
	        $bread_crumns .= "<span itemprop='name'>{$display_name}</span>";
	        $bread_crumns .= "</a>\n";
	        $bread_crumns .= "<meta itemprop='position' content='{$item_position_num}' />";
	        $bread_crumns .= "</li>\n";
	        ++$item_position_num;
	    }
	    $bread_crumns .= "</ol>\n";
	    return $bread_crumns;
	}

使い方としては下記を参考にどうぞ

view.php

	    $transition_list = [
            "TOP" => "/",
            "記事一覧" => "/posts",
            "記事" => "/post/1",
        ];
	    $bread_crumns = $this->bread_crumns_html($transition_list);
        print_r($bread_crumns);