数据库中的FILTER_VALIDATE_EMAIL和唯一电子邮件检查无效

I'm fairly new to the php scene, but as I have been searching for hours on what may be wrong with this code I am at a loss. For some reason, the FILTER_VALIDATE_EMAIL and unique email check in db are not working, they are being skipped completely. I know this because when the form is submitted it kicks out an error on the last I'm fairly new to the php scene, but as I have