Drupal 7自定义表单无法将字符串偏移量用作PHP7.2中的数组错误

我有一个定制的Drupal7表单，如下所示

   $form['general_details'] = array(
         '#type' => 'fieldset',
         '#title' => t('General'),
         '#description' => t('General Information.'),
         '#required' => TRUE,
         );

   $form['general_details']['salutation'] = array(
         '#type' => 'select',....

我在“$form['general_details']['saltation']行中遇到错误错误：无法将字符串偏移量用作PHP7.2的数组

有人能帮忙吗？

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提前感谢。

分配前必须声明空数组

 $form = array();

$form['general_details'] = array(
         '#type' => 'fieldset',
         '#title' => t('General'),
         '#description' => t('General Information.'),
         '#required' => TRUE,
);

$form['general_details']['salutation'] = array(
         '#type' => 'select',....