If you are new to PHP programming and wish to use your new found skills for an e-commerce site, you might do well to use an existing PHP-based e-commerce solution (e.g. Magento, Shopify, Zen Cart) instead of attempting to build your own from the ground up. This is especially true if you are on a deadline.
The truth is that while it is an excellent idea to practice your coding skills and not just learn in theory, the last thing you want is to go live with a buggy e-commerce site. This is true whether the e-commerce site sell something that people find as trivial as shoe strings or stuff that people are very particular about like wedding dresses and wedding rings. The point is that people who use the e-commerce site, both owner and customers, expect the site to work well so that nothing will go wrong with their purchases.
So practice all you want, but until you are sure that you can come up with a better solution than existing ones, then keep your efforts under wraps.
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