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This article mainly introduces "what are the main characteristics of PHP". In daily operation, I believe many people have doubts about the main characteristics of PHP. The editor consulted all kinds of materials and sorted out simple and easy-to-use methods of operation. I hope it will be helpful for you to answer the doubts about "what are the main characteristics of PHP?" Next, please follow the editor to study!

Brief introduction

PHP (hypertext preprocessor), originally an abbreviation for Personal Home Page, has been officially renamed to "PHP: Hypertext Preprocessor". Since the development of the Internet in China in the 1990s, Internet information has covered almost all the knowledge areas of our daily activities, and has gradually become an indispensable part of our life, study and work. According to statistics, since 2003, the size of web pages in China has basically doubled the growth rate, and showed an upward trend. As the most popular website program development language, PHP has the advantages of low cost, high speed, good portability and rich built-in function libraries, so it is used in website development by more and more enterprises. However, with the continuous upgrading of the Internet, there are many problems in PHP language.

According to the requirements of the dynamic website, as a language program, the specificity of PHP language gradually appears in the process of application, and its technical level will directly affect the running efficiency of the website. It is characterized by open source code and high similarity with general language such as C language in program design, so it is easy to understand and operable in the process of operation. At the same time, PHP language has a high level of data transmission and processing and output, and can be widely used in Windows systems and all kinds of Web servers. If the amount of data is large, PHP language can also broaden the link surface, connect with various databases, and alleviate the pressure of data storage, retrieval and maintenance. With the development of technology, PHP language search engine can also be tailored to implement personalized services, such as classified collection and storage according to customer preferences, which greatly improves the efficiency of data operation.

Main features

(1) Open source and free of charge

Because the source code of PHP's interpreter is public, websites with higher security factors can change the interpreter of PHP themselves. In addition, the use of the PHP runtime environment is also free.

(2) quickness

PHP is a language that is very easy to learn and use, its grammatical characteristics are similar to C language, but it does not have the complex address operation of C language, and it adds the concept of object-oriented, coupled with its concise grammar rules, which makes its operation and editing very simple and practical.

(3) the universality of database connections

PHP can establish connections with many mainstream databases, such as MySQL, ODBC, Oracle and so on. PHP uses different compiled functions to establish connections with these databases. PHPLIB is a commonly used base library for general affairs.

(4) process-oriented and object-oriented

In the use of PHP language, process-oriented and object-oriented can be used respectively, and PHP process-oriented and object-oriented can be mixed together, which is not possible in many other programming languages.

Advantages

(1) popular and easy to use

There is no doubt that PHP is the most popular programming language at present. It drives more than 200 million websites worldwide, and more than 81.7% of public websites around the world adopt PHP on the server side. The data structures commonly used in PHP are built-in, easy to use, not complicated at all, and the expression ability is quite flexible.

(2) there are many development positions.

PHP will make it easier for you to find a job in server-side website programming. Many Internet-related enterprises are using PHP development framework, so it can be said that the market demand for PHP development programmers is still relatively large.

(3) it is still developing continuously.

PHP is constantly compatible with technologies like closures and namespaces, while taking into account performance and current popular frameworks. Since version 7, it has been providing higher-performance applications.

(4) strong implantability

PHP language in the patch vulnerability upgrade process, the core part of the implantation is simple and easy, and the speed is fast.

(5) strong expansibility

In the process of database application, PHP language can call all kinds of data from the database and has high execution efficiency.

Shortcoming

(1) the interpretation and operation mechanism of PHP

In PHP, all variables are page-level, and both global variables and static members of the class are emptied after the page is executed.

(II) Design flaws, lack of attention to PHP is called an opaque language, because there is no stack trace, a variety of fragile inputs. There is no clear design philosophy. The early PHP was influenced by Perl, the standard library with out parameters was introduced by C language, and the object-oriented part was learned from C++ and Java.

(3) bad support for recursion

PHP is not good at recursion. It can tolerate a significantly less number of recursive functions than other languages.

PHP syntax comments:

/ /. Single-line comment

#. Single-line comment

/ *. * / Multiline comments

Variables:

The $array=NAME; variable name must start with a letter or an underscore, not a number, and no spaces in the middle! Case sensitive!

$xbirthday 5; $Xanti7; output to different results

Local variable

Parameter parameter scope

The difference between echo and print:

Echo "123,456", "789"; / / can output multiple strings in succession

Print "123"," 456 "; / / output error

Newline character:

Echo ""

Echo "\ n"

Echo PHP_EOL; / / newline character

Return variable type: var_dump

/ / spaces are also counted as a character

Strong reference and weak reference

Self-increasing and decreasing output

If condition judgment

Switch judgment

Array

Count gets the length of the array

Var_dump () returns the data type

Strlen (); returns the string length

Array (); create an array

$arrayname=array ('name' = > "icq",' age'= > 20 > true); / / associative array

Echo $arrayname ["name"]

$arrayName=array ('1century, "zhangsan", 20 # false, "beijingchangping"); / / numeric array

Echo $arrayName [3]; / / Boolean true print display 1

For iterates through the array:

Associative array:

Associative array 2:

Multidimensional array

Sort:

$GLOBALS-references all available variables in the global scope

PHP $_ REQUEST is used to collect data submitted by HTML forms

Name:

Loop:

Do while loop:

Function:

Classes and objects: the class − defines the abstract characteristics of a thing. The definition of the class includes the form of the data and the manipulation of the data. The object − is an instance of the class.

Super global variable:

$_ REQUEST can receive packets sent by GET POST

$_ SERVER ['PHP_SELF']; / / display header information

(isset ($name) & & isset ($pwd))

Isset detects whether the variable is set, not NULL

If the detected object is "" (empty), the return value is 1 false

Var_dump determines the data type

PHP constant

Use define (variable KEY (preferably uppercase), variable value,true/false,)

Define ("UNMBER", "this is a hacker"); / / cannot start with a $number

Reverse:

Cmd-- > php~\ php-r "phpinfo ();"

Php~\ php-f ".php file, which can be dragged to the CMD window"

$str1 = "123"

Echo $str1. = "456"

PHP form

HTML

Style selector:

.error {}

P {}

# ID {}

Echo htmlspecialchars (""); / / materialize the code output, ignoring the code output itself

Echo stripcslashes ("I\\ m abc"); / / remove the escape character

Trim removes the spaces at the left and right ends

Echo trim ("123")

Preg_match (/ matching expression / (to use regular expression), string to be matched). The return value is int (0 | 1) bool.

For matching, 1 false is returned, otherwise it is true 0

Echo preg_match ("/ php/", "you know the php is bester language")

! preg_match inversion

Delimiter must not be alphanumeric or backslash in delimiters cannot be alphanumeric and backslash.

Span combines inline elements class

The file contains: introduce some files to use the contents of the file.

There are four ways:

1. Include "File path / File name"

If a file error is introduced, a warning Warning will be reported, and subsequent code will still be executed.

2. Include_once "file"

The usage is basically the same as that of include, which only needs to be included once, and can be used all the time.

3. Require "file"

If the file is not found, an error ERROR will be reported when the file is included, and the subsequent code cannot be executed.

4. Require_once "file"

The usage is the same as require, it only needs to be included once, and it can be used all the time.

Directory jump is supported. You can use the relative path.. /.. /.. file or absolute path

Copy 1.png/b+1.txt/a 2.png

An is in ASCII format.

B indicates that the file is binary

Add the text file to the picture file.

The file contains, import some files to use the contents of the file, and the file contains four functions in PHP:

(1) include "File" / include ("File")

When you include a file, you will be warned if the included file cannot be found, and the subsequent code still knows

(2) include_once "document"

The usage is basically the same as that of include. You only need to include the file once, and you can use it all the time.

(3) require "document"

When a file is included, a fatal error will be reported if it is not found, and the subsequent code will not be executed

(4) require_once "document"

The usage is the same as that of require, and you only need to include the file once.

In the included file, if the code is written according to the standard syntax of PHP, the code will be executed; if it is not written in PHP syntax, it will be read out.

Copy 1.png/b+1.txt/a 2.png

An indicates that the file is in ASCII text format

B indicates that the file is binary

Php session Management

Session: the way or means by which data is transferred between the server and the user, and a channel needs to be established before the channel transmits data. Sessions are managed through cookie on the client and session on the server.

Comparison of cookie and session:

1. Cookie is stored in the user's browser and is set by the server through set-cookie in the return package. Cookie indicates the session state between the user's browser and the server. The cookie data can only be obtained after a successful login. The data is generally timely, and the user needs to log in again after expiration. With cookie data, users will bring cookie to each request, and the server will verify the validity and timeliness of the cookie. The sending of cookie needs to follow the same origin policy of the browser.

2. Session is stored on the server side, indicating the session state between the user and the server. Session and cookie correspond one to one, and the server also needs to remember which user logs into the site. In general, session is stored in the / tmp directory as a file, in the form of sess_XXXXX (for example: sess_nti62h7rrrnb5udpvfbad13cg5s9kqrm). At this time, the cookie assigned by the server to the browser is: nti62h7rrrnb5udpvfbad13cg5s9kqrm, as long as the value of the cookie has been modified. Then the server requires the user to log in again.

How to view cookie:

1. Enter _ javascript:alert ([xss_clean]) in the URL of the page you are currently logged in.

2. Enter: alert ([xss_clean]) or docunment.cookie in console

3. In the network management tools included in the browser.

Setcookie ("key", "123"); to be written before the HTML code.

Setcookie ("name", "456", time () + 5)

Echo $_ COOKIE ["name"]. "

"

Setcookie ("name", "value", time ()-3600); / / Delete cookie

Print_r ($_ COOKIE)

$_ SEESION ["id"] = 1

$_ SEESION ["demo"] = true

Unset ($_ SEESION ["id"]); / / Delete a value in seesion

Session_destroy (); / / clear all SEESION values

Session_start (); / / enable SESSION

Web developer plug-in

Fopen (how to open a file,):

R read only

R + read and write

W write mode to open, if the file does not exist, create a file

An additional content

A + read and append

$file=fopen ("test.txt", "a +")

Fread ($file,1024)

Feof (); detect whether the end of the file has been reached

Fclose ($NAME); close the process

Fopen (how to open a file,):

R read only

R + read and write

W write mode to open, if the file does not exist, create a file

An additional content

A + read and append, and create a file if it does not exist

$file=fopen ("test.txt", "a +")

Read a file

Fread ($file,1024); / / read the file

Feof (); detect whether the end of the file has been reached

Fgets ($file); / / read the file

While (! feof ($file)) {/ / determine whether the end is reached

Echo fgets ($file). "

"; / / read only one line at a time

}

While (! feof ($file)) {/ / determine whether the end is reached

Echo fgetc ($file). "

"; / / read only one line at a time

}

Unlink (); delete the file

Fclose ($NAME); close the process

Fputs ()

Echo file_get_contents ("123.txt"); read the file

Fputs (fopen ("1.php", "w"), "")

Echo file_get_contents ("1.php")

Stationmaster tools

$str= "PD9waHAgcGhwaW5mbygpOz8+"

$shell=base64_decode ($str)

Fputs (fopen ("ceshi.php", "w"), $shell)

Use base64_encode encryption base64_decode decryption

Fputs (fopen ("ceshi.php", "w"), base64_decode ("PD9waHAgJGV2YWw9KCRfUE9TVFsnayddKTs/Pg=="))

File line feeds\ n

At this point, the study on "what are the main characteristics of PHP" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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