<p>I have a PHP form (mortgage app) that is about 400 fields, traffic on the site will be low.</p>

<p>What is the ideal Session size for 400 fields going into a MySQL db?</p>

<p>In <code>php.ini</code> what do I set?</p>

<p>Anything I should set that I am missing?</p>

Well, personally I have had very large sessions before with very little problems. Probably the largest size I've had before is ~10MB. It's not optimal, but I haven't had a problem with slow scripts even with that size. I wouldn't worry about sessions getting to large, but I would try to keep it under control. My theory is, if keeping it in the session makes it much faster than quering the database every time (such as in the case of a search) then I go for it.