I understand that bitwise operations are necessary for much low-level programming, such as writing device drivers, low-level graphics, communications protocol packet assembly and decoding. I am doing PHP for several years now, I have seen bitwise operations very rarely in PHP projects.
Can you give me examples of usage?
Very little in PHP uses bitwise operations outside of optimization tricks as well as configuration such as error_reporting().
bitwise operation are extremely usefull in credentials info for example
function is_moderator($credentials)
{ return $credentials & 4; }
function is_admin($credentials)
{ return $credentials & 8; }
and so on... this way we can keep simple integer in 1 database column to have all credentials in system
You could use it for bitmasks to encode combinations of things. Basically, it works by giving each bit a meaning, so if you have 00000000, each bit represents something, in addition to being a single decimal number as well. Let's say I have some preferences for users I want to store, but my database is very limited in terms of storage. I could simply store the decimal number and derive from this, which preferences are selected, e.g. 9 is 2^3 + 2^0 is 00001001, so the user has preference 1 and preference 4.
00000000 Meaning Bin Dec | Examples
│││││││└ Preference 1 2^0 1 | Pref 1+2 is Dec 3 is 00000011
││││││└─ Preference 2 2^1 2 | Pref 1+8 is Dec 129 is 10000001
│││││└── Preference 3 2^2 4 | Pref 3,4+6 is Dec 44 is 00101100
││││└─── Preference 4 2^3 8 | all Prefs is Dec 255 is 11111111
│││└──── Preference 5 2^4 16 |
││└───── Preference 6 2^5 32 | etc ...
│└────── Preference 7 2^6 64 |
└─────── Preference 8 2^7 128 |
Further reading