Possible reason for items not being added to cart?

PHP
1

I am working on a website that has a problem i.e when you add things in cart. they don’t add. I was wondering to have some brain storming with SP community on what could be the possible reason who have worked on cart. and is there any easy online carts to use which is as good and up and running as implementing

2

Is this a custom cart script or a prebuilt library?

3

I don’t know. most probably phpcart

4

so far i have seen the live instance of site and it give out error
Can’t open file: ‘cart.MYI’ (errno: 145)
i googled and found out that its due to corruption in session. and remedy was to repair it. so i repair it. still i am downloading the site process but what else could be the problem
p.s the error shows up when u click add to cart