批量删除操作在Yii2中发生内部服务器错误

我在Yii2中有批量删除操作,下面是删除带有活动日志的记录的代码(这里DBMS是PostgreSQL)-

$companies = Yii::$app->request->post('ids', '');
if($companies && count($companies)) {
    foreach ($companies as $company) {
        try{
            $utsendelseid = $company['utsendelseid'];
            $mailid = $company['mailid'];

            $model = MailSend::find()->where(['utsendelseid' => $utsendelseid, 'mailid' => $mailid])->one();

            if($model && !$model->mailsendt) {
                if($model->delete()) {
                    // if model deleted successfully then keep a log using commandBus
                    $companyModel = $this->findCompanyModel($model->kundenr);
                    $questionnaireModel = $this->findModel($utsendelseid);

                    Yii::$app->commandBus->handle(new AddCompanyLogCommand([
                    'kundenr' => $model->kundenr,
                    'portal_id' => ($questionnaireModel?$questionnaireModel->prosjektkode:''),
                    'activity' => Yii::t('backend', 'Slettet fra spørreskjema'),
                    'notes' => Yii::t('backend', 'Company "{company}"  has been deleted from questionnaire - "{questionnaire}"("{questionnaire_id}")', [
                        'company' => ($companyModel?$companyModel->etternavn:''),
                        'questionnaire' => ($questionnaireModel?$questionnaireModel->beskrivelse:''),
                        'questionnaire_id' => $utsendelseid
                    ]),
                    'activity_type_code' => 30,
                    ]));
                }
            }
        }
        // even tried with PDOException
        catch(Exception $e){
            echo $e->getMessage();
            // exit the request processing here
            exit(0);
        }
    }
}

如果需要删除的记录数低于300,则此方法可以正常工作。如果记录数超过300,即使代码在try{}catch()块内,我也会收到内部服务器错误。我将max execution time设置为-1,max memory allocation设置为5120M,这现在不是问题所在。我认为这是一个连接错误太多的问题,而有那么多的SQL操作,因此,我在Yii2中启用持久连接,方法是 'attributes'=> [PDO::ATTR_PERSISTENT => true] . 但问题仍然存在。

我的问题是-

1. 为什么即使代码在try{}catch()块内,我仍会收到内部服务器错误?

2. 为什么它能工作到45秒?

3. 这是Apache杀死子进程的案例吗?

4. 是否存在允许运行查询的最大时间问题?

5. 如果这种情况下连接太多,那么为什么会出现持久连接问题?