Detailed explanation of commonly used operators and operation symbols in PHP_PHP Tutorial

/*Operation symbols (PHP) operation symbols
*
* According to the operation symbol function, it is divided into:
* 1. Arithmetic operators + - * / % ++ --
* 2. String operators. Connection operators
* 3. Assignment operator = += -= *= /= %= .=
* 4. Comparison operators > < >= <= == === != <> !==
* Comparison operators---conditional operators---relational operators
* There is only one result after comparison: boolean true false
* === When comparing, not only the content is required to be the same, but also the type is required to be the same
* !== When comparing, the contents are not the same, and the types are also required
* 5. Logical operators && or and || or or ! or not
* Logical operators can only operate on bool type values ​​and return bool type values ​​
* 6. Bitwise operators & | ^ ~ << >> >>>
* 7. Other operators ? : `` @ => -> :: & $
* `` Used to execute the operating system kernel
* @ Used to block error messages
* It is recommended to use "()" to change the priority of expressions
*
* % has two purposes: integer division operation; control range, do not use decimals or negative numbers
* % Convert the numbers on both sides of the operator to integers and then divide them to find the remainder.
*/

//Use % symbol to determine leap year

$year=2011;
if(($year%4==0 && %year%100!=0) || $year%400=0)
{
echo "run nian";
}
else
{
echo " not run nian";
}

// ++ --Usage of symbols
$a=10;
$a++; //$a=$a+1; Use variables first, then increment by 1
++$a; //$a=$a+1; First increment by 1, then use variable
$a--; //$a=$a-1; Use the variable first, then decrement it by 1
--$a; //$a=$a-1; Decrement it by 1 first, then use the variable
echo $a; //The result is 10

//++ -- Differences in operations

$a=10;
$b=$a++;//b=10,a=11
$c=--$b;//c=9,b=9
$d=$c++ + ++$c; //d=20,c=11
$e=$d-- - --$d; //d=18,e=2
echo $d;

//Usage of string operator .
$name="tom";
$age=27;
$height=1.75;
echo "My name is: {$name} My age is: {$age} My height is: {$height} meters
";
echo 'My name is: '.$name.' My age is: '.$age.' My height is: '.$height.'m'.'
';
echo "$age=".$age; //$age=27

echo "My name is: {$name} My age is: {$age} My height is: {$height} meters
";//Usage of assignment operator

$a=10;
$a+=10; //$a=$a+10;
$a-=10; //$a=$a-10;
$a*=10; //...
$a/=10; //...
$a%=10; //$a=$a%10;
$a.="abc";//$a=$a."abc";
echo $a;
$str='

';
$str.='';
$str.='';
$str.='';
$str.='

'; $str.='

';
echo $str;//Output a table

//Comparison operator
var_dump(15>6);//return bool(true)
$a=15;
if(15==$a)
{
echo "a=15";
}
else
{
echo "a!=15";
}

//Use of logical operators

var_dump(true && true);//true
var_dump(true && false);//false
var_dump(true || false);//true
var_dump(!true);//false
var_dump(!false);//true
//Determine username and password
$username="admin";
$password="123456";
$email="290080604@qq.com";
if($username=="admin" && $password="123456")
{
echo "Username and password are correct";
}
if($username=="" || $password=="" || $email=="")
{
echo "None of them can be empty";
}

//bit operator
$a=20; //00010100
$b=30; // 00011110
/*
* 20 00010100
* 30 00011110 &
*----------------------------------
* 00010100
*
*/
$c=$a & $b;
echo $c;

/*Additional, & | can also be used for logical operations
* Short circuit problem of && and ||:
* When && is performing an operation, if the previous number is false, then whether the following number is true, the entire expression is false, so the following operands will not be executed;
* ||During operation, if the previous number is true, then whether the following number is false, the entire expression is true, so the following operands will not be executed;
* However, when & or | are operated, both sides will be executed
*/
$a=10;
if($a>5 || $a++<100){}
echo $a;//output 10
$b=10;
if($b>5 | $b++<100){}
echo $b;//output 11

/*
The concept of bit: A bit is composed of 8 binary numbers (for example, 00000000),
A byte consists of 8 bits, so there are 32 binary numbers.

Original code: The highest bit uses 0 to represent positive numbers and 1 to represent negative numbers

+7 00000111
-7 10000111

Negative code: If a number is positive, its complement is the same as the original code;
If a number is negative, the sign bit is 1, and the remaining bits are the inversion of the original code;
+7 00000111
-7 11111000

+0 00000000
-0 11111111

Complement code: If a number is positive, its complement and inverse code are the same as the original code
If a number is negative, its complement = one's complement + 1, and the highest overflow bit is removed
       
-7 Original code 10000111 Reverse code 11111000
                                                     Complement code 11111001
                                                                         Given the complement of a negative number, convert it to decimal.
1. Let me disprove everyone first
2. Convert it to decimal number
3. Add the negative sign and subtract 1.

Example: complement code 11111010

              4+1=5
-5-1=-6
 
Bit operators:
& Bitwise AND |Bitwise OR ^Bitwise XOR ~Bitwise negation

Example: Bitwise AND 01101101

                  00100101
Conclusion: Only 1 1 is 1.
Bitwise OR 01101101
|00110111
                 01111111
Conclusion: Only 0 0 is 0.
​​Bitwise XOR 01101101
                ^00110111
                 01011010
Conclusion: It is 1 when there are only 1 0 or 0 1. (It can also be understood as 1 (true) in different states)
               Bitwise negation ~00110111
11001000
Conclusion: Change 0 to 1 and 1 to 0

Shift operator:
Left shift:<< Signed right shift:>> Unsigned right shift:>>>

Example: Number x x<<2 x>>2 x>>>2
17 00010001 01000100 00000100 00000100
-17 11101111 10111100 11111011 00111011
Conclusion: Positive numbers are padded with 0 when moving left and right, negative numbers are padded with 0 when moved left, signed right is padded with 1, and unsigned is padded with 0


*/

//Use of other operators
$a=10;
$b=$a>5 ? $a : 5;//Ternary operator, if true $b=$a otherwise $b=5
echo $b;

//Use `` to execute operating system shell commands
$str=`ipconfig /all`;
echo '

';<br>
echo $str;<br>
echo '

?>

This section lists the various operators used in PHP:

Arithmetic operators

Assignment operator

逻辑运算符