PHP mobile internet development notes (3) -- Operators and process control

I. PHP has a rich set of operators, most of which are directly from the C language. Operators can be divided into arithmetic operators, string operators, value assignment operators, bitwise operators, conditional operators, and logical operators. When various operators are in the same

I. PHP operators

PHP has a rich set of operators, most of which are directly from the C language. Operators can be divided into arithmetic operators, string operators, value assignment operators, bitwise operators, conditional operators, and logical operators. When operators are in the same expression, their operations have a certain priority.

(1) arithmetic operations

+-*/% + + --

(2) string operators

The character string operator has only one. (point), which is an English ending. It can connect a string to form a new string, or connect a string to a number. the type is automatically converted.

$ A = "dawanganban"; $ B = "123"; echo $ a. $ B; // output result: dawanganban123

(3) value assignment operator

= + =-= * =/= % =. =

$ A = "dawanganban"; $ a. = 1; $ a. = 2; $ a. = 3; echo $ a. $ B; // output result: dawanganban123

(4) bitwise operators

& | ~ ^ <>

(5) comparison operators

><>==! = <>==! =

<>: Not equal to or! = Same

===: Constant, equal value and consistent type

! ==: Non-constant, with inconsistent values or types

Echo 5 = "5"; // true PHP is a weak language (variables in js are similar) echo 5 = "5"; // false is completely equal

(6) logical operations

AND (logical AND) OR (logical OR) XOR (logical OR )&&(Logic and)|(Logical OR)! (Non-logical)

var_dump(5 && "");   //falsevar_dump(5 && "2"); //truevar_dump(5 || ""); //truevar_dump(0 xor 1); //truevar_dump(0 xor 0); //falsevar_dump(1 xor 1); //false

2. Process control

(1) if... else...

if(boolean){//TODO}

if(boolean){//TODO}else{//TODO}

if(boolean){//TODO}elseif(boolean){//TODO}elseif(boolean){//TODO}else{//TODO}

(2) switch

switch(expr){case expr1://TODObreak;case expr2://TODObreak;default://TODO}

(3) while loop

while(boolean){//TODOif(boolean) continue;if(boolean) break;}

(4) for loop

Break n; n indicates the number of bounce layers. the default value is 1.

Continum; indicates skipping a loop.