请尝试以下代码：

• • 在**中使用'default'键

$abc = array('1' => 'One','2'=> 'Two');
 echo  $this->Form->input('location_id',
                          'options' => $abc, 
                          default' =>$abc[1], 
                          ['empty' =>'Please select',
                          'required'=>'required', 
                          'class' => 'form-control',
                          'label'=>false]
                         );

• • 其中$abc [0]是要选定的项目的键**
• • 就像这样**

$options = array('M' => 'Male', 'F' => 'Female');
echo $this->Form->select('field', $options, array('default' => 'F'));

使用表单输入助手的value选项，如下所示：

$selected = 'india';
echo $this->Form->input('location_id', ['empty' =>'Please select', 'required'=>'required', 'class' => 'form-control', 'label'=>false, 'value'=> $selected]);

建议-阅读文档一次，然后开始开发。你将永远不会陷入这样简单的问题。并参考文档第一，当你陷入任何事情。

echo  $form->input('field_name', array(
            'type' => 'select',
    'options' => $arrayOfOptions, // typically set from $this->find('list') in controller 
    'label'=> 'Label name here',
    'value' => $arrProjectLeaderDetails['id'],  // specify default value 
    'escape' => false,  // prevent HTML being automatically escaped
    'error' => false,
    'class' => 'input_select_medium'
));

在cakephp4中：

echo $this->Form->select(
'field_name', [1,2,3,4,5,6],
['empty', => '(Click to select Something']
);

在文档中从这里向下滚动一点：https://book.cakephp.org/4/en/views/helpers/form.html#options-for-select-checkbox-and-radio-controls