CakePHP:使用optgroups在select上设置默认值

$this->set('options', [
    'Group 1' => [
        'value1' => 'Label 1',
        'value2' => 'Label 2',
    ],
    'Group 2' => [
        'value3' => 'Label 3',
        'value4' => 'Label 4',
    ],
]);

echo $this->Form->select('field_name', $options, [
    'empty' => '请选择',
    'multiple' => false,
    'value' => 'value2', // 设置默认值为value2
]);

echo $this->Form->select('field_name', $options, [
    'empty' => '请选择',
    'multiple' => false,
    'value' => 'value2', // 设置默认值为value2
    'optgroup' => true,
]);