Is Prestashop written in Object Oriented PHP? Best learning source

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Hi all,

I'm used to coding sites in PHP but just 'standard' PHP.

Looking at the php code for prestashop, it appears to be Object Oriented php
and quite frankly, looks incomprehensible to me!

So I guess I need a crash course in OO PHP.

Could anyone point me to a good source for moving over to and learning OO PHP?

Either book or online tutorials are fine.

Thanks!
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