Chapter II PHP basic PHP code Syntax _php Tutorial

I. Several styles of embedding PHP code in Web pages
Recommended for use in standard or short style
Copy CodeThe code is as follows:
Standard Style
Echo ' Hello world! ';
?>
Short style
Echo ' Hello world! ';
?>


two. Four ways to code comments
Copy CodeThe code is as follows:
Single-line Comment
/*
* Multi-line Comment
*/
#shell风格注释
/**
* Phpdoc Style Notes
*/
?>

three. Several ways to output strings to the browser
Copy CodeThe code is as follows:
/*
* Function of Echo function: output string to Browser
* Function return value: void
*/
Echo ' echo function! ';
Echo ('
');
/*
* Function of Echo function: output string to Browser
* Function return value: int
*/
print ' Print function ';
Echo ('
');
echo print ' echo value of print function. ';
Echo ('
');
/*
* Function of printf function: output string to Browser
* Function return Value: The length of the printed string
*/
printf ("A weekend has%d days", 7);
Echo ('
');
echo printf ("A weekend has%d days", 7);
Echo ('
');
/*
* Function of the sprintf function: Save the string in memory
* Function return Value: The saved string itself
*/
sprintf (' sprintf function ');
Echo ('
');
echo sprintf (' sprintf function ');
Echo ('
');
?>

Output Result:
echo function test!
Print function test.
Print function test. 1
A weekend has 7 days
A weekend has 7 days. 23
sprintf function test
Common Type Indicator

Type	Describe
%b	Integer, displayed as binary
%c	integer, shown as ASCII character
%d	Integer, displayed as a signed decimal number
%f	Floating-point numbers, displayed as floating-point numbers
%o	Integer, shown as octal number
%s	String, displayed as a string
%u	Integer, displayed as unsigned decimal number
%x	Integer that shows the hexadecimal number as lowercase
%x	Integer, hexadecimal number shown as uppercase

four. Identifiers and variables
1. Basic rules for identifiers:
1) An identifier can be any length and can consist of any letter, number, or underscore.
2) identifiers cannot begin with a number.
3) in PHP, identifiers are case-sensitive.
4) A variable name can be the same as a function name.
2. Variable assignment:
Copy CodeThe code is as follows:
$sum = 0;
$total = 1.22;
$sum = $total;
Echo $sum; 1.22
?>

3. The data type of the variable:
Basic data types

Type	Name
Integer	Integer
Float	Single-precision floating-point number
Double	Precision floating point number
String	String
Boolean	Boolean
Array	Array
Object	Object

4. Type strength
PHP is a dynamic language, is a very weak type of language, when the program runs, you can dynamically change the type of variables.
5. Type conversion:
Implicitly-Typed conversions:
Copy CodeThe code is as follows:
$sum = 0;
$total = 1.22;
$sum = $total;
Echo GetType ($sum);//double
?>

An explicit type conversion:
Copy CodeThe code is as follows:
$sum = 100;
$total = (string) $sum;
Echo GetType ($sum);//string
?>

Using the Settype () function for type conversion, the return value of 1 indicates success and NULL indicates failure.
Copy CodeThe code is as follows:
$sum = 58;
Echo Settype ($sum, "float");
Echo $sum; 58
Echo GetType ($sum); Double
?>

6. Functions for detecting variables:

Function	Function	return value
Gettype ()	Gets the type of the variable	One of the basic data types
Settype ()	Set the type of the variable	Bool (1:true 0:false (or "))
Isset ()	Used to determine whether a variable exists	Bool
Unset ()	Releases the given variable	Void
Empty ()	Detects whether the value of a variable is empty	Bool
Is_int () Is_integer ()	Detects if a variable is an integer	Bool
Is_string ()	Detects if a variable is a string	bool
Is_numeric	Detects if a variable is a numeric or numeric string	bool
Is_null	detects if the variable is NULL	bool
Intval ()	Gets the integer value of the variable	Int

Basic use of Isset ()
Copy CodeThe code is as follows:
$a = 10;
echo isset ($a);//1
?>
echo isset ($b);//'
?>

Basic use of Usset ()
Copy CodeThe code is as follows:
$a = 10;
unset ($a);
echo isset ($a);//'
?>

Basic use of Empty ()
Copy CodeThe code is as follows:
$a = 5;
$b = 1;
$c = 0;
$d = "";
$e = Array ();
$f = null;
$g = "0";
$h = false;
echo empty ($a);//' (FALSE)
Echo '
';
echo Empty ($b);//' (FALSE)
Echo '
';
echo Empty ($c);//1 (True)
Echo '
';
echo Empty ($d);//1 (True)
Echo '
';
echo Empty ($e);//1 (True)
Echo '
';
echo Empty ($f);//1 (True)
Echo '
';
echo Empty ($g);//1 (True)
Echo '
';
echo Empty ($h);//1 (True)
Echo '
';
echo Empty ($f);//1 (True)
?>

Basic use of is_int (). Similar functions are: Is_float (), is_double (), is_string (), Is_bool (), Is_array (), Is_null (), Is_long (), Is_object (), Is_resource (), Is_numeric (), is_real () and so on.
Copy CodeThe code is as follows:
$a = 11;
$b = 1.23;
$c = 3.1415926;
$d = "Hello";
$e = false;
$f = Array ();
$g = null;
echo is_int ($a);//1
Echo '
';
echo is_float ($b);//1
Echo '
';
echo is_double ($c);//1
Echo '
';
echo is_string ($d);//1
Echo '
';
echo Is_bool ($e);//1
Echo '
';
echo Is_array ($f);//1
Echo '
';
echo Is_null ($g);//1
Echo '
';
echo is_numeric ($a);//1
?>

Basic use of the intval () function. Similar functions are: Floatval (), Strval ()
Copy CodeThe code is as follows:
$a = 22.23;
Echo GetType ($a);//double
Echo '
';
$b = intval ($a);//Type after conversion does not change the original type of $ A
Echo GetType ($a);//double
Echo '
';
?>
$a = 22.23;
Echo GetType ($a);//double
Echo '
';
Settype ($a, "integer");//Type conversion will change $AA original type
Echo GetType ($a);//integer
Echo '
';
?>

7. Scope of variables

Super Global variables

Variable name	Role
$GLOBALS	All global variable arrays
$_server	Array of server environment variables
$_get	Array of variables passed to the script by Get method
$_post	Array of variables passed to the script by post
$_cookie	Array of cookie variables
$_files	Array of variables related to file uploads
$_env	Array of environment variables
$_request	Array of variables used by the user input
$_session	Array of Session Variables

8. Constants
Once defined, it cannot be changed again.
Copy CodeThe code is as follows:
Define ("Total", 100);
Echo total;//100
Echo '
';
Define ("Total", 200);
Echo total;//100
?>

Ways to view the predefined constants of PHP
Copy CodeThe code is as follows:
Phpinfo ();
?>

Methods for referencing PHP predefined constants
Copy CodeThe code is as follows:
echo $_server["SERVER_NAME"];//localhost
Echo '
';
echo $_server["Server_port"];//8090
Echo '
';
echo $_server["Document_root"];//d:/appserv/www
Echo '
';
?>

Five. Accessing form variables
Three common ways
Copy CodeThe code is as follows:
echo $username;//short style, easy to confuse with variable name, not recommended.
Echo '
';
echo $_post[' username '];//medium style, 4.1. Post 0 support, recommended
Echo '
';
echo $HTTP _post_vars[' username '];//lengthy style, obsolete, may be removed in the future
?>

Posttest.html
Copy CodeThe code is as follows:




<title>How to get form data</title>






Six. String connection.
Copy CodeThe code is as follows:
echo "The Student name is:". $_post[' username ');
echo "
";
echo "Welcome to". " School ";
?>

http://www.bkjia.com/PHPjc/324815.html www.bkjia.com true http://www.bkjia.com/PHPjc/324815.html techarticle I. Several styles of embedding PHP code in Web pages recommend using standard style or short style copy code code as follows:? PHP//Standard style echo ' Hello world! ';??//Short style echo ' ...

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