Chapter 3 php operators and control structure code

Source: Internet
Author: User

I. String insertion
Difference between double quotation marks and single quotation marks:
1. Use of double quotation marks:
Copy codeThe Code is as follows:
<Meta http-equiv = "Content-Type" content = "text/html; charset = UTF-8">
<? Php
// Double quotation marks can parse variables and escape characters
$ Username = "jack ";
Echo "his name is $ username! ";
Echo "<br/> ";
$ Username = "Xiaodong ";
// If the exclamation point is in English, the variable will be parsed normally.
Echo "His name is $ username! "; // His name is Xiaodong!
Echo "<br/> ";
// If it is a Chinese exclamation point, it cannot be parsed.
Echo "His name is $ username! "; // His name is
Echo "<br/> ";
// Although the escape characters are parsed here, \ n is a line break in the source code.
// Only one character is displayed in the browser
Echo "His name is $ username, \ n he is 20 years old this year"; // his name is Xiao Dong, he is 20 years old this year
Echo "<br/> ";
// To avoid errors, string connection is recommended.
Echo "His name is". $ username. "He is 20 years old."; // his name is Xiaodong. He is 20 years old.
?>

2. Use of single quotes:
Copy codeThe Code is as follows:
<? Php
// Single quotes only output the string literal value,
// The variables and escape characters are not parsed.
// The syntax is not highlighted.
$ Username = 'anllin ';
Echo 'his name is $ username, \ n his age is 20 .';
// Output
// His name is $ username, \ n his age is 20.
?>

Some common escape characters

Escape Sequence

Description

\ N

Line Break

\ R

Enter

\ T

Horizontal tabulation chart

\\

Backslash

\ $

Dollar sign

\"

Double quotation marks


Ii. Operators
Copy codeThe Code is as follows:
<? Php
// Arithmetic Operator
$ A = 5;
$ B = 3;
Echo $ a + $ B;
Echo '<br/> ';
Echo $ a-$ B;
Echo '<br/> ';
Echo $ a * $ B;
Echo '<br/> ';
Echo $ a/$ B;
Echo '<br/> ';
Echo $ a % $ B;
?>

8
2
15
1.66666666667
2
Copy codeThe Code is as follows:
<? Php
// Compound value assignment operator
$ A = 5;
$ B = 3;
Echo $ a + = $ B;
Echo '<br/> ';
Echo $ a-= $ B;
Echo '<br/> ';
Echo $ a * = $ B;
Echo '<br/> ';
Echo $ a/= $ B;
Echo '<br/> ';
Echo $ a % = $ B;
Echo '<br/> ';
Echo $ a. = $ B;
?>

8
5
15
5
2
23
Copy codeThe Code is as follows:
<? Php
// Increment/decrease Operator
$ A = 5;
Echo ++ $;
Echo '<br/> ';
Echo $ a ++;
Echo '<br/> ';
Echo -- $;
Echo '<br/> ';
Echo $ --;
?>

6
6
6
6
Copy codeThe Code is as follows:
<? Php
$ A = 5;
$ B = 3;
$ C = 5;
$ D = '5 ';
Echo $ a = $ c;
Echo '<br/> ';
Echo $ a ===$ c;
Echo '<br/> ';
Echo $ a = $ d;
Echo '<br/> ';
Echo $! = $ B;
Echo '<br/> ';
Echo $! ==$ D;
Echo '<br/> ';
Echo $! = $ B;
Echo '<br/> ';
Echo $ a> $ B;
Echo '<br/> ';
Echo $ B <$ c;
Echo '<br/> ';
Echo $ a >=$ c;
Echo '<br/> ';
Echo $ a <= $ c;
?>

1
1
1
1
1
1
1
1
1
1
Copy codeThe Code is as follows:
<? Php
$ A = false;
Echo! $;
Echo '<br/> ';
$ B = 5;
$ C = 3;
Echo $ B> 0 & $ c> 0;
Echo '<br/> ';
Echo $ B> 0 and $ c> 0;
Echo '<br/> ';
Echo $ B! = 0 | $ c! = 0;
Echo '<br/> ';
Echo $ B! = 0 or $ c! = 0;
Echo '<br/> ';
?>

1
1
1
1
1
The "and" or "operator has a lower priority than & |
Ternary Operators
Copy codeThe Code is as follows:
<? Php
$ A = 100;
Echo $ a> 60? 'Success': 'fail ';
?>

Success
Error suppression Operator
Copy codeThe Code is as follows:
<? Php
Echo @ (1, 100/0 );
?>

 

 

Iii. Control Structure
If condition judgment statement
Copy codeThe Code is as follows:
<Meta http-equiv = "content-type" content = "text/html; charset = UTF-8"/>
<? Php
$ A = 10;
If ($ a> 0)
{
Echo 'integer greater than 0 ';
}
Echo '<br/> ';
If ($ a> 0)
{
Echo 'integer greater than 0 ';
}
Else if ($ a <0)
{
Echo 'integer less than 0 ';
}
Else
{
Echo 'integer equal to zero ';
}
?>

Switch statement
Copy codeThe Code is as follows:
<Meta http-equiv = "content-type" content = "text/html; charset = UTF-8"/>
<? Php
$ Role = 'admin ';
Switch ($ role)
{
Case 'admin ':
Echo 'admin ';
Break;
Case 'user ':
Echo 'normal user ';
Break;
Case 'guest ':
Echo 'tourists ';
Break;
Default:
Echo 'tourists ';
Break;
}
?>

While loop statement
Copy codeThe Code is as follows:
<? Php
$ A = 10;
While ($ a> 0)
{
Echo $ --;
Echo '<br> ';
}
?>

Do while LOOP statement
Copy codeThe Code is as follows:
<? Php
$ A = 10;
Do
{
Echo $ --;
Echo '<br/> ';
}
While ($ a> 0)
?>

For Loop statement
Copy codeThe Code is as follows:
<? Php
For ($ a = 0; $ a <10; $ a ++)
{
Echo $;
Echo '<br/> ';
}
?>

Break statement
Copy codeThe Code is as follows:
<Meta http-equiv = "content-type" content = "text/html; charset = UTF-8"/>
<? Php
For ($ a = 0; $ a <10; $ a ++)
{
Echo $;
Echo '<br/> ';
If ($ a = 5)
{
Break; // terminate the loop, but the statement after the loop is executed
}
}
Echo 'loop termination ';
?>

Exit statement
Copy codeThe Code is as follows:
<? Php
For ($ a = 0; $ a <10; $ a ++)
{
Echo $;
Echo '<br/> ';
If ($ a = 5)
{
Exit; // exit directly. The statement following the loop is not executed.
}
}
Echo 'loop termination ';
?>

Continue statement
Copy codeThe Code is as follows:
<? Php
For ($ a = 0; $ a <10; $ a ++)
{
Echo $;
Echo '<br/> ';
If ($ a = 5)
{
Continue; // end the loop and continue the next loop. The statement after the loop is still executed.
}
}
Echo 'loop termination ';
?>

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