Zend framework Zend DbTable add where in if（）语句

我通过以下方式获取数据：

$table = new Application_Model_DbTable_FooBar();

$data = $table
->select()
->where('id = ?', (int) $id)
->query()
->fetchAll();

并希望在if（）语句中添加单独的where子句。
诸如此类：

if($foo == "bar") {
    $data->where('foo = ?, 'bar');
}

所以我尝试了类似的方法，但没有成功

$table = new Application_Model_DbTable_FooBar();

$table
->select()
->where('id = ?', (int) $id);

if($foo == "bar") {
    $table->where('foo = ?, 'bar');
}

$data = $table->query()->fetchAll();

试试这个

$table = new Application_Model_DbTable_FooBar();

$table = $table
->select()
->where('id = ?', (int) $id);

if($foo == "bar") {
    $table = $table->where('foo = ?, 'bar');
}

$data = $table->query()->fetchAll();