您可以先实例化数组，也可以选择填充它，然后将其传递给add_query_arg() 功能如下：

$url_query_args = array();

if( isset( $search ) ) {
    $url_query_args[\'search\'] = $search;
}

if( isset( $category ) ) {
    $url_query_args[\'category\'] = $category;
}

if( isset( $filter ) ) {
    $url_query_args[\'filter\'] = $filter;
}

esc_url( add_query_arg( $url_query_args, \'/site\' ) );

$url_query_args = array();
$possible_args  = array(
    \'search\',
    \'category\',
    \'filter\',
);

foreach( $possible_args as $arg ) {

    if( ! isset( ${$arg} ) ) {
        continue;
    }

    $url_query_args[ $arg ] = ${$arg};

}

esc_url( add_query_arg( $url_query_args, \'/site\' ) );