Detailed introduction to php operators and expressions

Operators and expressions are the most basic knowledge in learning PHP. This article explains some applications and techniques of operators and expressions in PHP through examples, as well as what needs to be paid attention to. Friends in need can refer to it. one time.

php Operators and expressions

1. Classification of operators

1. By operand Category

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 operator

1.==, ===(constantly equal to), !=, !===, <>(not equal to), <, >, <=, >=

(5) Logical operators
1.// The ones inside the brackets have higher priority than those outside the brackets
2.&&(and), ||(or), !(not), xor (XOR),

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

2. Arithmetic operator

% remainder, common usage : 1) Divisibility operation 2) Controlling 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)

// %会把两边的数转成整型后在整除
// %两边不能用小数或负数
if ((($year%4 == 0) && ($year%100 != 0)) || $year%400 == 0)
echo "闰年";
else
echo "平年";

3. Assignment operator

//先自身加10，然后赋值给自己，等价于 $a=$a+10
$a += 10;
 
//前置递增递减，先递增递减再赋值
++$a

//先赋值，再递增递减
$a++ 
//实例
$a = 10;
$b = $a++
$c = --$b
结果：a=11 b=9 c=9

4. Logical operator

xor XOR: The same is false (two true or two false = false), different is true (one true and one false = false)
Tips: Pay attention to the difference with or, two or True = true
Logical operator short circuit
1, && //If one is false, then no operation will be performed later, it must be false
2, || //If one is true, then no operation will be performed later, it must be false True

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

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

5. Bit operators

Bit operations: convert integers to 32-bit binary, and convert strings to ANSCA codes for processing

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