Price comparison website backend technology and affiliate earning share tracking? How to build meta search engine?

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PHP

e-commerce

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I am wondering how exact price comparison website will work.??? I have read asked questions available on stackoverflow but no answer helped in answering my queries.

Can anybody have complete idea how exactly it works? Which platform/language/any CMS(or script)/backend is used by top price comparison website?

I found several websites which share their earning with users if they purchase through them via affiliate links. How exactly do they track particular users if there is no provision of confirming user from affiliate provider(merchant) end?

Does amazon offer verification of particular user who is purchasing through affiliate link?

As per my research on internet, web spidering techniques are being used nowadays but they are being done.

How meta search engine work and how can it be built up?

Thank you