PHP implements dynamic random verification code mechanism

php implements dynamic random verification code mechanism

CAPTCHA is the abbreviation of "Completely Automated Public Turing test to tell Computers and Humans Apart". It is a public fully automated program that distinguishes whether the user is a computer or a human. It can prevent: malicious cracking of passwords, ticket fraud, forum flooding, and effectively prevents a hacker from using a specific program to brute force a specific registered user to continuously log in. 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 humans can answer it. Since computers cannot answer CAPTCHA questions, the user who answers the questions can be considered a human.

The production of dynamic verification codes in Php is based on the image processing of PHP. Let’s first introduce the image processing of PHP.

1.Introduction to php image processing

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

header('Content-Type: image/png;');

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 )

$im = imagecreatetruecolor(200,200);

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 )

$blue = imagecolorallocate($im,0,102,255);

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

imagefill($im,0,0,$blue);

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

Color Filler

$white = imagecolorallocate($im,255,255,255);

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 )

imageline($im,0,0,200,200,$white);

imageline($im,200,0,0,200,$white);

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 )

imagestring($im,5,66,20,'jingwhale',$white);

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 ] )

imagepng($im);

The sixth step is to clear all resources

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

imagedestroy($im);

Graphics created by calling other pages (html)

The sample code is as follows:

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//The first step is to set the file MIME type

header('Content-Type: image/png;');

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

$im = imagecreatetruecolor(200,200);

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

$blue = imagecolorallocate($im,0,102,255);

imagefill($im,0,0,$blue);

//Step 4, enter some lines, text, etc. on the blue background

$white = imagecolorallocate($im,255,255,255);

imageline($im,0,0,200,200,$white);

imageline($im,200,0,0,200,$white);

imagestring($im,5,66,20,'Jing.Whale',$white);

//Step 5, output the final graphic

imagepng($im);

//Step six, I want to clear all resources

imagedestroy($im);

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Display effect:

image

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

for ($i=0;$i<$_rnd_code;$i++) {

$_nmsg .= dechex(mt_rand(0,15));

}

string dechex (int $number), returns a string containing the hexadecimal representation of the given number parameter.

2) Save in session

$_SESSION['code'] = $_nms

3) Create pictures

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//Create an image

$_img = imagecreatetruecolor($_width,$_height);

//White

$_white = imagecolorallocate($_img,255,255,255);

//Filling

imagefill($_img,0,0,$_white);

if ($_flag) {

//Black, border

$_black = imagecolorallocate($_img,0,0,0);

imagerectangle($_img,0,0,$_width-1,$_height-1,$_black);

}

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4) Blurred background

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//Draw 6 lines randomly

for ($i=0;$i<6;$i++) {

$_rnd_color = imagecolorallocate($_img,mt_rand(0,255),mt_rand(0,255),mt_rand(0,255));

imageline($_img,mt_rand(0,$_width),mt_rand(0,$_height),mt_rand(0,$_width),mt_rand(0,$_height),$_rnd_color);

}

//Random snowflakes

for ($i=0;$i<100;$i++) {

$_rnd_color = imagecolorallocate($_img,mt_rand(200,255),mt_rand(200,255),mt_rand(200,255));

imagestring($_img,1,mt_rand(1,$_width),mt_rand(1,$_height),'*',$_rnd_color);

}

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5) Output and destruction

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//Output verification code

for ($i=0;$i

$_rnd_color = imagecolorallocate($_img,mt_rand(0,100),mt_rand(0,150),mt_rand(0,200));

imagestring($_img,5,$i*$_width/$_rnd_code+mt_rand(1,10),mt_rand(1,$_height/2),$_SESSION['code'][$i],$_rnd_color );

}

//Output image

header('Content-Type: image/png');

imagepng($_img);

//Destroy

imagedestroy($_img);

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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:

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/**

* This is a freeware

* $Id: global.func.php 2015-02-05 20:53:56 jingwhale$

/**

* _code() is the verification code function

* @access public

* @param int $_width Verification code length: 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)

* @return void This function generates a verification code after execution

function _code($_width = 75,$_height = 25,$_rnd_code = 4,$_flag = false) {

//Create random code

for ($i=0;$i<$_rnd_code;$i++) {

$_nmsg .= dechex(mt_rand(0,15));

}

//Save in session

$_SESSION['code'] = $_nmsg;

//Create an image

$_img = imagecreatetruecolor($_width,$_height);

//White

$_white = imagecolorallocate($_img,255,255,255);

//Fill

imagefill($_img,0,0,$_white);

if ($_flag) {

//Black, border

$_black = imagecolorallocate($_img,0,0,0);

imagerectangle($_img,0,0,$_width-1,$_height-1,$_black);

}

//Draw 6 lines immediately

for ($i=0;$i<6;$i++) {

$_rnd_color = imagecolorallocate($_img,mt_rand(0,255),mt_rand(0,255),mt_rand(0,255));

imageline($_img,mt_rand(0,$_width),mt_rand(0,$_height),mt_rand(0,$_width),mt_rand(0,$_height),$_rnd_color);

}

//Snowflakes will follow soon

for ($i=0;$i<100;$i++) {

$_rnd_color = imagecolorallocate($_img,mt_rand(200,255),mt_rand(200,255),mt_rand(200,255));

imagestring($_img,1,mt_rand(1,$_width),mt_rand(1,$_height),'*',$_rnd_color);

}

//Output verification code

for ($i=0;$i

$_rnd_color = imagecolorallocate($_img,mt_rand(0,100),mt_rand(0,150),mt_rand(0,200));

imagestring($_img,5,$i*$_width/$_rnd_code+mt_rand(1,10),mt_rand(1,$_height/2),$_SESSION['code'][$i],$_rnd_color );

}

//Output image

header('Content-Type: image/png');

imagepng($_img);

//Destroy

imagedestroy($_img);

}

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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

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/**

* 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');

verification code

验证码：

复制代码

显示如下：

image

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();

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/**

* This is a freeware

* $Id: codeimg.php 2015-02-05 20:53:56 jingwhale$

//开启session

session_start();

//引入全局函数库（自定义）

require dirname(__FILE__).'/includes/global.func.php';

//运行验证码函数。通过数据库的_code方法，设置验证码的各种属性,生成图片

_code(125,25,6,false);

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image

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：

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/**

* 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');

//开启session

session_start();

//引入全局函数库（自定义）

require dirname(__FILE__).'/includes/global.func.php';

//检验验证码

if ($_GET['action'] == 'verification') {

if (!($_POST['code'] == $_SESSION['code'])) {

_alert_back('验证码不正确!');

}else{

_alert_back('验证码通过！');

}

verification code

& lt; dd & gt; verification code: & lt; input type = "text" name = "code" class = "code" /& gt; & lt; img src = "codeimg.php" id = "codeimg" /& g. t; & lt ;/dd>

& lt; dd & gt; & lt; input type = "submit" class = "submit" value = "verification" /& gt; & lt; /dd & gt;

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

If you want to update the verification code above, you must refresh the page; we write a codeimg.js function to update the verification code by clicking on the verification code image

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window.onload = function () {

var code = document.getElementById('codeimg');//Find the img tag in html by id

code.onclick = function () {//Add a click event to the label

this.src='codeimg.php?tm='+Math.random();//Modify time and redirect to codeimg.php

};

}

Related labels：

dynamic mechanism

source：php.cn

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