I can't see where they handle prices of stuff correctly. As far as I can tell, they are treating prices as floats. You shouldn't treat prices as floats, or you get weird rounding errors sometimes. This is unacceptable when dealing with money.
PHP is terrible for e-commerce where it halts on large business transactions, and terrible money handling and its lack of typing and other ecommerce APIs. PHP lacks fine-tuned IO service control, even node-v8 lacks this. Also that facade pattern is disgusting, another reason to avoid PHP.<p>Use CLR or JVM where you can control IO services and long-running tasks much better.