Detailed explanation of bit operators in php

Bitwise OperatorsAllows the evaluation and operation of specified bits in an integer.

The bits in phpOperators are in the following table

## ExampleNameResult##$a >> $b Shift the bits in to the right times (each shift means "divide by 2"). Displacement is a mathematical operation in PHP. Bits moved out in any direction are discarded. When shifting left, the right side is padded with zeros, and the sign bit is moved away, meaning that the sign is not preserved. When shifting right, the left side is padded with sign bits, which means the sign is preserved.

##$a & $b And (bitwise AND)	will set the bits in the sum that are both 1 to 1.
$a | $b Or (bitwise OR)	will sum the Any bit that is 1 is set to 1.
$a ^ $b Xor (bitwise exclusive OR)	will sum The bit in which one is 1 and the other is 0 is set to 1.
~ $a Not (bitwise negation)	will be 0 Bit is set to 1 and vice versa.
$a << $b Shift left	Shift the bits in to the left times (each shift means "multiply by 2").
Shift right

Pay attention to the conversion of
data type

. If both the left and right arguments are

strings, then the bitwise operators will operate on the ASCII values ​​of the characters. PHP's ini setting

error_reporting

uses bitwise values, provides a real example of turning off a certain bit. To display all errors except prompt level
, use this in php.ini: E_ALL & ~E_NOTICE

Four common bitwise operators: & (bitwise And), | (bitwise OR), ^ (bitwise XOR), ~ (bitwise negation)

##& (Bitwise AND): When the corresponding bits are both 1, it is 1 after the & operation, otherwise it is 0| (Bitwise OR): When one of the corresponding bits is 1, it is 1 after the | operation. is 1, and when both are 0, it is 0

^ (bitwise XOR): When the corresponding bits are not 1 at the same time, they are 1 after the ^ operation; when they are 0 at the same time, they are 0, and they are 1 at the same time. After the ^ operation, it is also 0

~ (bitwise negation): $a+(~$a)=-1

In computers, negative numbers are expressed in the complement form of their positive values. .

Here we need to know three concepts, original code, inverse code and complement code.

Original code: An integer, converted into a binary number according to its absolute value, is called the original code. The original code of

8 is: 0000 0000 0000 0000 0000 0000 0000 1000

Inverse code: The binary number is bit-wise inverted, and the resulting new binary number is called the one's complement of the original binary number. . Negation operation means: 1 becomes 0, 0 becomes 1.

8 Bitwise negation: 1111 1111 1111 1111 1111 1111 1111 0111

Complement code: The complement code plus 1 is called complement code. That is to say, to get the complement of a number, first get the complement, then add 1 to the complement, and the resulting number is called the complement.

The complement of a positive number is the same as its original code; the complement of a negative number is to add 1 to the last digit of its complement

The complement of the complement is added by 1: 1000 0000 0000 0000 0000 0000 000 1001; This gives you the complement form of the positive value of a negative number. That is -9.

Example

<?php
$m=8;
$n=12;
$p=-109;
$mn=$m&$n;
echo $mn."<br>";
$mn=$m|$n;
echo $mn."<br>";
$mn=$m^$n;
echo $mn."<br>";
$mn=~$m;
echo $mn."<br>";
$mn=~$p;
echo $mn."<br>";
?>

Output result:

8
12
4
-9
108

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