September 2016
Intermediate to advanced
332 pages
6h 20m
English
Content preview from Modular Programming with PHP 7Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Liskov substitution principle
The Liskov substitution principle talks about inheritance. It specifies how we should design our classes so that client dependencies can be replaced by subclasses without the client seeing the difference, as per the definition found on Wikipedia:
"objects in a program should be replaceable with instances of their subtypes without altering the correctness of that program"
While there might be some specific functionality added to the subclass, it has to conform to the same behavior as its base class. Otherwise the Liskov principle is violated.
When it comes to PHP and sub-classing, we have to look beyond simple concrete classes and differentiate: concrete class, abstract class, and interface. Each of the three can be ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.