"yes i know. bt there several issues with blockchain"

Unless you say what they are, nobody can help. Their documentation is clear, with examples. The remainder of your post is incomprehensible.

but am just using bitpay to check payment. and the problem is not that. my problem is to update the script if payment received and to perform other actions

and am sure this bitpay api doesn't require documentation coz is open to use with just single post command. its easier than blockchain ur talking about

"but am just using bitpay to check payment."

You're not checking payments properly, see my first reply.

"my problem is to update the script if payment received and to perform other actions"

Already discussed, your approach is wrong. If the browser window closes, everything is gone, because you don't properly record anything.