您应该在HTML表单文本字段中检查什么？

I'm writing a PHP script to grab text box data from a submitted form. These are simple text boxes and I don't want to accept any HTML tags. I think I should at least use strip_tags() and addslashes(). Anything else? I wouldn't mind restricting the input to alphanumerics, should I use a regular expression to seek out nonstandard characters?I'm writing a PHP script to grab text box data