PHP and MySQL Program design "Fourth Edition" chapter Three essays--(1)

Chapter Three Basics of PHP

(3.1--3.5)

　　3.1 Embed PHP code in a Web page

Default syntax: <?php?>

Short tags: <??> or <?= "";? >--Not recommended

Script: <script language= "PHP" ></script>

ASP style: <%%>

　　3.2 Adding comments to the Code

Single-line C + + syntax://

Shell syntax: #

Multi-line C syntax:/*

This

That

*/

　　3.3 outputting data to the browser

Print (): 1.print ()

2.print ""

Echo (): 1.echo ()

2.echo ""

printf (): Interger printf (string format [, mixed args])

printf () facilitates the output of mixed products consisting of static text and dynamic information stored in one or more variables

printf ("Bar inventory:%d bottles of tonic water." 100)//output: Bar inventory:100 bottles of tonic water.

sprintf (): String sprintf (String format[, mixed arguments])

The sprint () function functions the same as printf (), but it assigns the output to a string rather than directly to the browser

$cost = sprintf ("$%.2f", 43.2); $cost = $43.20

P.S Common Type indicators

%b the argument as an integer, displayed as a binary number

%c considers the argument to be an integer that is displayed as the corresponding ASCII character

%d considers the argument to be an integer, displayed as a signed decimal number

%f the parameter as a floating-point number, displayed as a floating-point number

%o The argument is considered an integer, which is displayed as an octal number

%s considers the argument to be a string, displayed as a string

%u considers the parameter to be an integer and is displayed as an unsigned decimal number

%x considers the argument to be an integer, which is displayed as a lowercase hexadecimal number

%x considers the argument to be an integer, which is shown in uppercase hexadecimal number

　　3.4 Data types supported by PHP

A data type (datatype) is a generic term for data with a set of identical attributes.

Common types of data include:

Boolean: Returns True or false, case insensitive. Available 0 for false, non-0 value indicates true

Shaping: Decimal, octal, hex

Floating point: Also known as single-precision, double-precision, or real-numbers can specify numbers that contain fractional parts

String: In short, a string is a sequential sequence of characters, usually defined in single or double quotation marks

Conformance data types include:

Array: Two-dimensional array, multidimensional array

Object: The object must be displayed for declaration. The behavior of declaring object properties is done in class.

In-depth objects:

classAppliance {Private $_power; functionSetpower ($status){        $this->_power =$status; }}...$blender=NewAppliance;/*The class definition creates some properties and functions related to the data structure (appliance here), and appliance has only one property power, which can be modified with setpower (). A class definition is a template that cannot be manipulated by itself, and objects are created based on this template. This is done with the new keyword. So the last line creates an object of class appliance, called Blender, so that you can use Setpower () to set the power properties of the Blender object: $blender->setpower ("on")*/

Use type casting to implement conversions between data types:

P.S Type conversion operator

Conversion operator to

Arrays (Array)

(bool) or (Boolean) Boolean value

(int) or (integer) integer value

(object) objects

(real) or (double) or (float) floating-point number

(String) string

Type auto-conversion: PHP is very loosely defined for type definitions, and sometimes the variables are automatically converted to integer types based on the environment in which they are referenced.

Types-related functions:

Get Type: GetType () Form: String GetType (mixed Var)

Conversion type: Settype () Form: Boolean settype (mixed var,string type)

Type identifier function: Form: Boolean is_name (mixed Var)

　　3.5 identifiers

A valid identifier must meet the following properties:

Start with a letter or underscore

Can only consist of letters, numbers, underscore characters, and other ASCII characters from 127~255

Case sensitive

Any length

The identifier name cannot be the same as any PHP pre-defined keyword.

PHP and MySQL Program design "Fourth Edition" chapter Three essays--(1)