Create dynamic random verification code in php, php dynamic verification code_PHP tutorial

php generates dynamic random verification code, php dynamic verification code

CAPTCHA is the abbreviation of "Completely Automated Public Turing test to tell Computers and Humans Apart". It is a public fully automated test to distinguish whether a user is a computer or a human. program. It can prevent: malicious cracking of passwords, ticket fraud, forum flooding, and effectively prevents a hacker from using a specific program to violently crack a specific registered user from making continuous login attempts. In fact, using verification codes is a common method for many websites now. We use This function is implemented in a relatively simple way.

This question can be generated and judged by a computer, but only a human can answer it. Since computers cannot answer CAPTCHA questions, the user who answers the questions can be considered a human.

Php’s dynamic verification code production is based on php’s image processing. Let’s first introduce php’s image processing.

1.php image processing introduction

In PHP5, processing dynamic images is much easier than before. PHP5 includes the GD extension package in the php.ini file. You only need to remove the corresponding comments of the GD extension package to use it normally. The GD library included in PHP5 is the upgraded GD2 library, which contains some useful JPG functions that support true color image processing.

Generally generated graphics are stored in PHP’s document format, but dynamic graphics can be obtained directly through HTML’s image insertion method SRC. For example, verification code, watermark, thumbnail, etc.

General process for creating images:

1). Set the header to tell the browser the MIME type you want to generate.

2). Create an image area, and all subsequent operations will be based on this image area.

3). Draw a filled background in the blank image area.

4). Draw graphic outlines on the background to enter text.

5). Output the final graphics.

6). Clear all resources.

7). Call images from other pages.

The first step is to set the file MIME type and output type. Change the output type to image stream

Generally generated images can be png, jpeg, gif, wbmp

The second step is to create a graphics area and image background

imagecreatetruecolor() returns an image identifier representing a black image of size x_size and y_size. Syntax: resource imagecreatetruecolor ( int $width , int $height )

The third step is to draw a filled background in the blank image area

Requires a color filler; imagecolorallocate -- assigns a color to an image; syntax: int imagecolorallocate ( resource $image , int $red , int $green , int $blue )

Fill this blue color into the background; imagefill -- area filling; syntax: bool imagefill ( resource $image , int $x , int $y , int $color )

The fourth step is to enter some lines, text, etc. on the blue background

Color Filler

Draw two line segments: imageline

imageline() draws a line segment in the image image from coordinates x1, y1 to x2, y2 (the upper left corner of the image is 0, 0) using color color. Syntax: bool imageline ( resource $image , int $x1 , int $y1 , int $x2 , int $y2 , int $color )

Draw a line of string horizontally: imagestring

imagestring() uses col color to draw the string s to the x, y coordinates of the image represented by image (this is the coordinate of the upper left corner of the string, and the upper left corner of the entire image is 0, 0). If font is 1, 2, 3, 4 or 5, the built-in font is used. Syntax: bool imagestring ( resource $image , int $font , int $x , int $y , string $s , int $col )

Step 5, output the final graphics

imagepng() Outputs a GD image stream (image) in PNG format to standard output (usually a browser), or to a file if filename is given. Syntax: bool imagepng ( resource $image [, string $filename ] )

The sixth step is to clear all resources

imagedestroy() releases the memory associated with image. Syntax: bool imagedestroy ( resource $image )

Graphics created by calling other pages (html)

The sample code is as follows:

Display effect:

2. Create dynamic verification code

Attachment: Code source address https://github.com/cnblogs-/php-captcha

1. Create a picture with verification code and blur the background

The random code uses hexadecimal; the blurred background means adding lines, snowflakes, etc. to the background of the picture.

1) Create random code

2) Save in session

3) Create pictures

4) Blurred background

5) Output and destruction

Encapsulate it in the global.func.php global function library, and the function name is _code() for easy calling. We will set the four parameters $_width, $_height, $_rnd_code, $_flag to enhance the flexibility of the function.

* @param int $_width The length of the verification code: if you want 6 digits, 75+50 is recommended; if you want 8 digits, 75+50+50 is recommended, and so on
* @param int $_height The height of the verification code
* @param int $_rnd_code The number of digits in the verification code
* @param bool $_flag Whether the verification code requires a border: true with border, false without border (default)

The encapsulated code is as follows:

2. Create a verification mechanism

Create a PHP verification page and check whether the verification code is consistent through session.

1) Create verification-code.php verification page

/**
 *      [verification-code] (C)2015-2100 jingwhale.
 *
 *      This is a freeware
 *      $Id: verification-code.php 2015-02-05 20:53:56 jingwhale$
 */
//设置字符集编码
header('Content-Type: text/html; charset=utf-8');
?>



   
   
   

   

       

           

               

验证码：

               

           

       

   

显示如下：

2）创建产生验证码图片页面

创建codeimg.php为verification-code.php html代码里的img提供验证码图片

首先必须在codeimg.php页面开启session；

其次，将我们封装好的global.func.php全局函数库引入进来；

最后，运行_code();

3）创建session检验机制

首先必须在verification-code.php页面也开启session；

其次，设计提交验证码的方式，本文以get方式提交，当action=verification时提交成功；

最后，创建验证函数，原理是将客户端用户提交的验证码同服务器codeimg.php中session的验证码是否一致；这里有一个js弹窗函数_alert_back()，我们也把它封装在global.func.php里；

修改verification-code.php中php代码如下：

/**
 *      [verification-code] (C)2015-2100 jingwhale.
 *
 *      This is a freeware
 *      $Id: verification-code.php 2015-02-05 20:53:56 jingwhale$
 */
//Set character set encoding
header('Content-Type: text/html; charset=utf-8');
//Open session
session_start();
//Introduce global function library (custom)
require dirname(__FILE__).'/includes/global.func.php';
//Check verification code
if ($_GET['action'] == 'verification') {
If (!($_POST['code'] == $_SESSION['code'])) {
​​​​ _alert_back('Verification code is incorrect!');
}else{
​​​​ _alert_back('Verification code passed!');
}
}
?>

         

                                                                                       

Verification code:                                                                                                                                                                                           out out out there out there out out out there out of the way,

                                                              
                         

3. Click on the verification code image to update the verification code