我正在使用以下函数创建一个下拉搜索表单，并用名为“grades”的自定义分类法的术语填充它。下拉列表用于搜索，但我不知道如何添加selected 将类别设置为所选术语。请参见下面我的函数中的变量$SEARCHEDTERM -- 如何使其等于搜索的项？

function get_terms_grades_dropdown() {

    $myterms = get_terms(\'grades\');
    $output = "";
    foreach ($myterms as $term) {     
        $term_taxonomy = $term->taxonomy;
        $term_slug = $term->slug;
        $term_name = $term->name;
        $value = $term->term_id;
        if ($SEARCHEDTERM == $term->slug) {
            $selected = "selected=\'selected\'";
        } else {
            $selected = \'\';
        }
        $output .= "<option value=\'" . $value . "\' " . $selected . ">" . $term_name . "</option>";
    }

    return $output;
}