What are bitwise shift (bit-shift) operators and how do they work?

Question

I\'ve been attempting to learn C in my spare time, and other languages (C#, Java, etc.) have the same concept (and often the same operators) ...

What I\'m wondering

Answer 1

Be aware of that only 32 bit version of PHP is available on the Windows platform.

Then if you for instance shift << or >> more than by 31 bits, results are unexpectable. Usually the original number instead of zeros will be returned, and it can be a really tricky bug.

Of course if you use 64 bit version of PHP (Unix), you should avoid shifting by more than 63 bits. However, for instance, MySQL uses the 64-bit BIGINT, so there should not be any compatibility problems.

UPDATE: From PHP 7 Windows, PHP builds are finally able to use full 64 bit integers: The size of an integer is platform-dependent, although a maximum value of about two billion is the usual value (that's 32 bits signed). 64-bit platforms usually have a maximum value of about 9E18, except on Windows prior to PHP 7, where it was always 32 bit.