Javascript CakePHP从表单获取数据

我试图以cakephp形式获取输入数据的值，以便在sql查询中使用它来自动填充其他数据。目前我正在尝试使用$this->request->data，但当我更改客户时，它不会显示任何结果。我想让它显示选中的客户，但目前它只是空白。不确定我是否试图正确获取数据或显示数据不正确

<div class="invoices form large-9 medium-8 columns content">
    <?= $this->Form->create($invoice) ?>
    <fieldset>
        <legend><?= __('Add Invoice') ?></legend>
        <?php

            echo $this->Form->input('customer_id', ['options' => $customers, 'empty' => true,'id'=>'customers']);        ?>

    </fieldset>
    <?= $this->Form->button(__('Submit')) ?>
    <?= $this->Form->end() ?>
</div>


<script>
            document.getElementById('customers').addEventListener('change',function(){
                alert(<?php echo $this->request->data('customers');
                ?>)
                });

            </script>

我的add.ctp

<div class="invoices form large-9 medium-8 columns content">
    <?= $this->Form->create($invoice) ?>
    <fieldset>
        <legend><?= __('Add Invoice') ?></legend>
        <?php

            echo $this->Form->input('customer_id', ['options' => $customers, 'empty' => true,'id'=>'customers']);        ?>

    </fieldset>
    <?= $this->Form->button(__('Submit')) ?>
    <?= $this->Form->end() ?>
</div>


<script>
            document.getElementById('customers').addEventListener('change',function(){
                alert(<?php echo $this->request->data('customers');
                ?>)
                });

            </script>

document.getElementById（'customers'）。addEventListener（'change'，function（）{
警报（）
});

用此代码替换您的代码

<div class="invoices form large-9 medium-8 columns content">
    <?= $this->Form->create($invoice) ?>
    <fieldset>
        <legend><?= __('Add Invoice') ?></legend>
        <?php

            echo $this->Form->input('customer_id', ['options' => $customers, 'empty' => true,'id'=>'customers']);        ?>

    </fieldset>
    <?= $this->Form->button(__('Submit')) ?>
    <?= $this->Form->end() ?>
</div>


<script>
            document.getElementById('customers').addEventListener('change',function(){
                alert(<?php echo $this->request->data('customers');
                ?>)
                });

            </script>

document.getElementById('customers').addEventListener('change',function(){
       alert(this.value);
 });

---

您是否检查了此视图中是否真的设置了

$this->request->data（'customers'）