What does this ~ operator mean here?

Question

Example:

set_error_handler(array($this, 'handleError'), E_ALL & ~E_STRICT & ~E_WARNING & ~E_NOTICE);

what does that suppose to mean?

Answer 1

It is the bitwise not operator (also called "complement"). That is the bits set in ~ $a are those that are not set in $a.

So then

E_ALL & ~E_STRICT & ~E_WARNING & ~E_NOTICE

is the bits set in E_ALL and those not set in E_STRICT, E_WARNING and E_NOTICE. This basically says all errors except strict, warning and notice errors.

Answer 2

It's the bitwise-not operator. For example the bitwise negation of a number with binary representation 01011110 would be 10100001; every single bit is flipped to its opposite.

Answer 3

The distinction between bitwise (&, |, ~) and non-bitwise (&&, ||, !) operators is that bitwise are applied across all bits in the integer, while non-bitwise treat an integer as a single "true" (non-zero) or "false" (zero) value.

Say, $flag_1 = 00000001 and $flag_2 = 00000010. Both would be "true" for non-bitwise operations, ($flag_1 && $flag_2 is "true"), while the result of $flag_1 & $flag_2 would be 00000000 and the result of $flag_1 | $flag_2 would be 00000011. ~$flag_2 would be 11111101, which when bitwise-ANDed to a running result would clear that bit position (xxxxxx0x). $flag_2 bitwise-ORed to a running result would set that bit position (xxxxxx1x).

Answer 4

See Bitwise Operators : it's the "not" operator (quoting) :

~ $a
Bits that are set in $a are not set, and vice versa.

Which means, taking an example inspired from what you posted, that this portion of code :

var_dump(decbin(E_STRICT));
var_dump(decbin(~E_STRICT));

Will get you this output :

string '100000000000' (length=12)
string '11111111111111111111011111111111' (length=32)

(Add a couple of 0 for padding on the left of the first line, and you'll see what I mean)

Removing the padding from the second output, you get :

100000000000
011111111111

Which means the ~ operator gave a 0 bit for each bit that was equal to 1 in the intput -- and vice-versa,

Answer 5

It's the not bitwise operator. Read about bitwise operators here:

http://php.net/manual/en/language.operators.bitwise.php