Detailed introduction to expressions and operators in php

php Operators and expressions

1. Classification of operators

1. Classification by operand

1.!true // Unary operator
2.$a+$b // Binary operator
3.true ? 1:0 // Ternary operator

2. Classification by operation function

(1) Arithmetic operators
1.+, -, x, /, % (remainder)

(2)String operator
1.. // For example: $a = 'abc'.'efg';

(3) Assignment operator

1.= // Simple assignment
2.+=, -=, X=, /=, %=, .= // Compound assignment
3. ++($a++, ++$a), --($a--, --$a) // Increment and decrement
4.&($a = 1;$b = &a) // Reference assignment

(4)Comparison operators

1.==, ===(equal to), !=, !===, <>( Not equal to), <, >, <=, >=

(5) Logical operator
1.// Ratio in parentheses Exceptions have high priority
2.&&(and), ||(or), !(not), xor(exclusive or),

(6)bit operators
1.& (bitwise AND), | (bitwise OR), ~ (bitwise NOT), ^ (bitwise XOR), << (left shift), >> (right shift)

2. Arithmetic operator

% remainder, common usage: 1) Integer division operation 2) Control the value range

Example: Determine whether it is a leap year (one leap year every four years, no leap years, and another leap year after four hundred years)

// % will convert the numbers on both sides into integers and then divide them
/ / % cannot use decimals or negative numbers on both sides
if ((($year%4 == 0) && ($year%100 != 0)) || $year%400 == 0)
echo "Leap year ";
else
echo "平年";

3. Assignment operator

//First add 10 to itself, and then assign it to Self, equivalent to $a=$a+10
$a += 10;

//Prefix increment and decrement, first increment and decrement and then assign value
++$a

//Assign value first, then increment and decrement
$a++
//Example
$a = 10;
$b = $a++
$c = --$b
Result: a=11 b=9 c=9

##4. Logical operators

xor exclusive or: the same is false (two true or two false = false), different values ​​are true (one true and one false = false)

Tips: Pay attention to the difference from or, or two true = true
Logical operator short circuit
1, && //One is false, then If no operation is performed later, it must be false
2, || //If one is true, then if no operation is performed later, it must be true

fopen ("test.php","r") or die(" Failed");

Tips: There is no short-circuit feature for operator & |

5. Bit operator

Bit operation: Convert integer type It is a 32-bit binary, and the string is converted to ANSCA code for processing

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