PHP Learning note--3. operator

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PHP Learning note--1. variables

PHP Learning note--2. Constants

PHP Learning note--3. operator

1. Arithmetic operators

+-*/% (modulo)

%: The positive and negative values of the remainder are determined by dividend

2. Comparison operators

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

= = = The value and type of the variable is compared to!==

Note: When comparing different types

PHP will first convert the previous variable to the same type as the Sing Woo, then compare

Boolean-string true-> ' 1 ' false-> "

String--Number ' 123abc456 '->123

String--Boolean ' or ' 0 '->false

Number, Boolean 0 or 0.0->false negative also true

Numeric-string As-is output

3. String Operators . (stitching)

$str 1 = ' Hello '; $str 2 = "; $str 3 = ' world '; Echo $str 1. $str 2. $str 3;    // Hello world//Note: $str 1 than Echo, $str 2, $str 3; more efficient, eliminating the stitching process

4. Assignment Operators =

5. Logical operators

|| (or) && (with)! (anti) XOR (XOR)

①&& (and) priority is higher than | | Or

Use parentheses to make logic clearer when ② multiple conditions

③xor (XOR) means that a true one must be false and the return value is True

④ The conditional judgment in a logical way,

when a condition is established (or)/not established (with), the latter condition is no longer judged , which is called the ' short circuit characteristic '

// Example: $a = 3; $b = 5; if (($a = 8) | | ($b = 9)) {    $a++    ; $b+ +;} Echo $a,$b;    // 9 6//Note: $b = 9 in the condition is not judged

6. Ternary operators ?:

Condition? Statement 1: Statement 2;

Execute statement 1 when condition is true

Execute Statement 2 when condition is false

NOTE: The If statement is also achievable and more efficient

7. Bitwise operators //understanding

& (with) | (or) ^ (XOR) << (shift left) >> (shift right)

Take 0 as false, and each one does the operation with, or, or XOR

Example: 12&5 =>4

0000 1100

5 = 0000 0101
-----------------
4 =>0000 0100

Example: 5<<1 =>10

5 =>0000 0101
-----------------
Ten =>0000 1010

Example: 5>>1 =>2

5 =>0000 0101
-----------------

2 = 0000 0010

8. Supplemental Knowledge //understanding

① binary

Only 0 12 cardinality

Example: 16+0+0+2+0

From high to Low 4 3 2 1 0

10010

Then the decimal 18 is converted to binary 0001 0010

② octal

Base is 0~7

Add 0,php to the number before the output is eight binary

Example: 023 =>19

Note: When 0239 is present, because the octal number is only possible between 0~7,

So PHP will ignore 9, still output 19

③ Hex

Base for 0~9 a~f =>0~15

Add 0x,php to the number before the output is 16 binary

Example: 0x1c =>28

@zhnoah
Source: http://www.cnblogs.com/zhnoah/
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PHP Learning note--3. operator