search
HomeBackend DevelopmentPHP TutorialHow to use PHP GD library to generate verification code_PHP tutorial

How to use PHP GD library to generate verification code_PHP tutorial

Jul 15, 2016 pm 01:28 PM
phpphp.iniuseIncreasehowLibraryQuoteusgeneratecodewantuseverify

When we want to use , first add a line of reference in php.ini: extension=php_gd2.dll

Restart apache. Make a test page var_dump(gd_info()); the output data shows that the PHP GD library is successfully referenced.

form auth.html

<ol class="dp-xml">
<li class="alt"><span><strong><font color="#006699"><span class="tag"><span class="tag-name">html</span><span class="tag">></span></span></font></strong><span> </span></span></li>
<li class="">
<span></span><strong><font color="#006699"><span class="tag"><span class="tag-name">head</span><span class="tag">></span></span></font></strong><span> </span>
</li>
<li class="alt">
<span></span><strong><font color="#006699"><span class="tag"><span class="tag-name">meta</span></span></font></strong><span> </span><span class="attribute"><font color="#ff0000">http-equiv</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">'Content-Type'</font></span><span> </span><span class="attribute"><font color="#ff0000">content</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">'text/html; charset=utf-8'</font></span><span class="tag"><strong><font color="#006699">></font></strong></span><span> </span>
</li>
<li class="">
<span></span><strong><font color="#006699"><span class="tag"><span class="tag-name">title</span><span class="tag">></span></span></font></strong><span>验证码</span><strong><font color="#006699"><span class="tag"></span><span class="tag-name">title</span><span class="tag">></span></font></strong><span> </span>
</li>
<li class="alt">
<span></span><strong><font color="#006699"><span class="tag"></span><span class="tag-name">head</span><span class="tag">></span></font></strong><span> </span>
</li>
<li class="">
<span></span><strong><font color="#006699"><span class="tag"><span class="tag-name">body</span><span class="tag">></span></span></font></strong><span> </span>
</li>
<li class="alt">
<span></span><strong><font color="#006699"><span class="tag"><span class="tag-name">h1</span><span class="tag">></span></span></font></strong><span>请输入验证码</span><strong><font color="#006699"><span class="tag"></span><span class="tag-name">h1</span><span class="tag">></span></font></strong><span> </span>
</li>
<li class="">
<span></span><strong><font color="#006699"><span class="tag"><span class="tag-name">form</span></span></font></strong><span> </span><span class="attribute"><font color="#ff0000">action</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">"check_auth.php"</font></span><span> </span><span class="attribute"><font color="#ff0000">method</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">"post"</font></span><span class="tag"><strong><font color="#006699">></font></strong></span><span> </span>
</li>
<li class="alt">
<span>   </span><strong><font color="#006699"><span class="tag"><span class="tag-name">input</span></span></font></strong><span> </span><span class="attribute"><font color="#ff0000">name</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">"auth"</font></span><span> </span><span class="attribute"><font color="#ff0000">type</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">"text"</font></span><span class="tag"><strong><font color="#006699">></font></strong></span><span> </span>
</li>
<li class="">
<span>   </span><strong><font color="#006699"><span class="tag"><span class="tag-name">img</span></span></font></strong><span> </span><span class="attribute"><font color="#ff0000">src</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">"auth.php"</font></span><span> </span><span class="attribute"><font color="#ff0000">border</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">"0"</font></span><span> </span><span class="tag"><strong><font color="#006699">/></font></strong></span><span> </span>
</li>
<li class="alt">
<span>   </span><strong><font color="#006699"><span class="tag"><span class="tag-name">input</span></span></font></strong><span> </span><span class="attribute"><font color="#ff0000">type</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">"submit"</font></span><span> </span><span class="attribute"><font color="#ff0000">value</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">"提交"</font></span><span class="tag"><strong><font color="#006699">></font></strong></span><span> </span>
</li>
<li class="">
<span></span><strong><font color="#006699"><span class="tag"></span><span class="tag-name">form</span><span class="tag">></span></font></strong><span> </span>
</li>
<li class="alt">
<span></span><strong><font color="#006699"><span class="tag"></span><span class="tag-name">body</span><span class="tag">></span></font></strong><span> </span>
</li>
<li class="">
<span></span><strong><font color="#006699"><span class="tag"></span><span class="tag-name">html</span><span class="tag">></span></font></strong><span> </span>
</li>
</ol>

PHP GD library generates verification code auth.php

<ol class="dp-xml">
<li class="alt"><span><strong><font color="#006699"><span class="tag"></span><span class="tag-name">php</span></font></strong><span> </span></span></li>
<li class=""><span>   session_start();  </span></li>
<li class="alt"><span>   header("Content-type:image/png");  </span></li>
<li class=""><span> </span></li>
<li class="alt">
<span>   $</span><span class="attribute"><font color="#ff0000">img_width</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">100</font></span><span>;  </span>
</li>
<li class="">
<span>   $</span><span class="attribute"><font color="#ff0000">img_height</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">20</font></span><span>;  </span>
</li>
<li class="alt"><span> </span></li>
<li class=""><span>   srand(microtime()*100000);  </span></li>
<li class="alt">
<span>   for($</span><span class="attribute"><font color="#ff0000">i</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">0</font></span><span>;$i</span><strong><font color="#006699"><span class="tag"><span class="tag-name">4</span></span></font></strong><span>;$i++)  </span>
</li>
<li class=""><span>   {  </span></li>
<li class="alt">
<span>        $</span><span class="attribute"><font color="#ff0000">new_number.</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">dechex</font></span><span>(rand(0,15));  </span>
</li>
<li class=""><span>   }  </span></li>
<li class="alt"><span> </span></li>
<li class=""><span>   $_SESSION[check_auth]=$new_number;  </span></li>
<li class="alt">
<span>   $</span><span class="attribute"><font color="#ff0000">new_number</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">imageCreate</font></span><span>($img_width,$img_height);//创建图象  </span>
</li>
<li class=""><span>   ImageColorAllocate($new_number,255,255,255);  //设置背景色为白色  </span></li>
<li class="alt"><span> </span></li>
<li class="">
<span>   for($</span><span class="attribute"><font color="#ff0000">i</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">0</font></span><span>;$i</span><strong><font color="#006699"><span class="tag"><span class="tag-name">strlen</span></span></font></strong><span>($_SESSION[check_auth]);$i++)  </span>
</li>
<li class="alt"><span>   {  </span></li>
<li class="">
<span>       $</span><span class="attribute"><font color="#ff0000">font</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">mt_rand</font></span><span>(3,5);  </span>
</li>
<li class="alt">
<span>       $</span><span class="attribute"><font color="#ff0000">x</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">mt_rand</font></span><span>(1,8) + $img_width*$i/4;  </span>
</li>
<li class="">
<span>       $</span><span class="attribute"><font color="#ff0000">y</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">mt_rand</font></span><span>(1,$img_height/4);  </span>
</li>
<li class="alt">
<span>       $</span><span class="attribute"><font color="#ff0000">color</font></span><span>=</span><span class="attribute-value"><font color="#0000ff">imageColorAllocate</font></span><span>($new_number,mt_rand(0,100),mt_rand(0,150),mt_rand(0,200));//设置字符颜色  </span>
</li>
<li class=""><span>       imageString($new_number,$font,$x,$y,$_SESSION[check_auth][$i],$color);//输出字符  </span></li>
<li class="alt"><span>   }  </span></li>
<li class=""><span> </span></li>
<li class="alt"><span>   ImagePng($new_number);  </span></li>
<li class=""><span>   ImageDestroy($new_number);  </span></li>
<li class="alt">
<span></span><span class="tag"><strong><font color="#006699">?></font></strong></span><span> </span>
</li>
</ol>

PHP GD library submission page check_auth.php

<ol class="dp-xml">
<li class="alt"><span><strong><font color="#006699"><span class="tag"></span><span class="tag-name">php</span></font></strong><span> </span></span></li>
<li class=""><span>   session_start();  </span></li>
<li class="alt">
<span>   $</span><span class="attribute"><font color="#ff0000">auth</font></span><span>=$_POST['auth'];  </span>
</li>
<li class=""><span> </span></li>
<li class="alt"><span>   if(empty($auth))  </span></li>
<li class=""><span>   {  </span></li>
<li class="alt"><span>       echo '错误:验证码不能为空';  </span></li>
<li class=""><span>       die;  </span></li>
<li class="alt"><span>   }  </span></li>
<li class=""><span> </span></li>
<li class="alt">
<span>   if($</span><span class="attribute"><font color="#ff0000">auth</font></span><span>==$_SESSION['check_auth'])  </span>
</li>
<li class=""><span>   {  </span></li>
<li class="alt"><span>       echo '正确';  </span></li>
<li class=""><span>   }  </span></li>
<li class="alt"><span>   else  </span></li>
<li class=""><span>   {  </span></li>
<li class="alt"><span>       echo '错误:验证码输入错误';  </span></li>
<li class=""><span>   }  </span></li>
<li class="alt">
<span></span><span class="tag"><strong><font color="#006699">?></font></strong></span><span> </span>
</li>
</ol>

The above is the relevant knowledge about generating verification codes by the PHP GD library introduced in this article. I hope it will be helpful to everyone.


www.bkjia.comtruehttp: //www.bkjia.com/PHPjc/446427.htmlTechArticleWhen we want to use it, first add a line of reference in php.ini: extension=php_gd2.dll and restart apache. Make a test page var_dump(gd_info()); the output data shows that the PHP GD library is successfully referenced. Form...
Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
How can you check if a PHP session has already started?How can you check if a PHP session has already started?Apr 30, 2025 am 12:20 AM

In PHP, you can use session_status() or session_id() to check whether the session has started. 1) Use the session_status() function. If PHP_SESSION_ACTIVE is returned, the session has been started. 2) Use the session_id() function, if a non-empty string is returned, the session has been started. Both methods can effectively check the session state, and choosing which method to use depends on the PHP version and personal preferences.

Describe a scenario where using sessions is essential in a web application.Describe a scenario where using sessions is essential in a web application.Apr 30, 2025 am 12:16 AM

Sessionsarevitalinwebapplications,especiallyfore-commerceplatforms.Theymaintainuserdataacrossrequests,crucialforshoppingcarts,authentication,andpersonalization.InFlask,sessionscanbeimplementedusingsimplecodetomanageuserloginsanddatapersistence.

How can you manage concurrent session access in PHP?How can you manage concurrent session access in PHP?Apr 30, 2025 am 12:11 AM

Managing concurrent session access in PHP can be done by the following methods: 1. Use the database to store session data, 2. Use Redis or Memcached, 3. Implement a session locking strategy. These methods help ensure data consistency and improve concurrency performance.

What are the limitations of using PHP sessions?What are the limitations of using PHP sessions?Apr 30, 2025 am 12:04 AM

PHPsessionshaveseverallimitations:1)Storageconstraintscanleadtoperformanceissues;2)Securityvulnerabilitieslikesessionfixationattacksexist;3)Scalabilityischallengingduetoserver-specificstorage;4)Sessionexpirationmanagementcanbeproblematic;5)Datapersis

Explain how load balancing affects session management and how to address it.Explain how load balancing affects session management and how to address it.Apr 29, 2025 am 12:42 AM

Load balancing affects session management, but can be resolved with session replication, session stickiness, and centralized session storage. 1. Session Replication Copy session data between servers. 2. Session stickiness directs user requests to the same server. 3. Centralized session storage uses independent servers such as Redis to store session data to ensure data sharing.

Explain the concept of session locking.Explain the concept of session locking.Apr 29, 2025 am 12:39 AM

Sessionlockingisatechniqueusedtoensureauser'ssessionremainsexclusivetooneuseratatime.Itiscrucialforpreventingdatacorruptionandsecuritybreachesinmulti-userapplications.Sessionlockingisimplementedusingserver-sidelockingmechanisms,suchasReentrantLockinJ

Are there any alternatives to PHP sessions?Are there any alternatives to PHP sessions?Apr 29, 2025 am 12:36 AM

Alternatives to PHP sessions include Cookies, Token-based Authentication, Database-based Sessions, and Redis/Memcached. 1.Cookies manage sessions by storing data on the client, which is simple but low in security. 2.Token-based Authentication uses tokens to verify users, which is highly secure but requires additional logic. 3.Database-basedSessions stores data in the database, which has good scalability but may affect performance. 4. Redis/Memcached uses distributed cache to improve performance and scalability, but requires additional matching

Define the term 'session hijacking' in the context of PHP.Define the term 'session hijacking' in the context of PHP.Apr 29, 2025 am 12:33 AM

Sessionhijacking refers to an attacker impersonating a user by obtaining the user's sessionID. Prevention methods include: 1) encrypting communication using HTTPS; 2) verifying the source of the sessionID; 3) using a secure sessionID generation algorithm; 4) regularly updating the sessionID.

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

WebStorm Mac version

WebStorm Mac version

Useful JavaScript development tools