Yes, running the above expression in PHP, and in a lot of other languages, will confirm that 0.1 + 0.2 does not equal to 0.3.
But this weird behavior is explainable and even justified.
Floating point numbers can open you up a completely new universe.
Provided of course that they are properly used.
This talk will go through a bit of theory, and a lot of concrete examples.
From the Gulf War to the Quake graphics engine, via the Ariane 5 space rocket, we will see the benefits and the potential dangers of using floating-point numbers.
From these examples, we will extract some lessons we can translate into our day to day development practices.
And finally, the talk will cover when to use floating-point numbers, and when to avoid them, like when managing prices or billing, and what are the alternatives in those cases.