Use php to implement website verification code function [recommended by bloggers] and php Verification Code
Verification code is a common security measure for websites and a skill that is difficult for new webmasters. Here I will introduce you to a simple and effective verification code implementation method.
Before getting started
Before the official start, we need to open the php gd2 graphics library support (in php. ini, search "php_gd2.dll" and find";Extension = php_gd2.dll "and remove the semicolon from the beginning of the sentence ).
You can refer to: how to open the php gd2 Library
Core: img. php
This page generates a verification code and writes the correct valueSession
Random 4-digit Verification Code
$ Check = rand );
Write the generated verification code to the session
Session_start ();
$ _ SESSION ["check"] = $ check;
Create an image
$ Im = imagecreate (80, 30 );
Because the background of this image is black by default, we need to fill it with white.
Imagefill ($ im, 255,255,255, ImageColorAllocate ($ im ));
Use imageline to randomly draw two solid lines
$ Y1 = rand (0, 30 );
$ Y2 = rand (0, 30 );
$ Y3 = rand (0, 30 );
$ Y4 = rand (0, 30 );
Imageline ($ im, 0, $ y1, 70, $ y3, 000 );
Imageline ($ im, 0, $ y2, 70, $ y4, 000 );
Draw text at random locations
$ Strx = rand (3, 15 );
$ Stry = rand (2, 15 );
Imagestring ($ img, 5, $ strx, $ stry, substr ($ check, 100), ImageColorAllocate ($ img ));
$ Strx + = rand (15, 20 );
$ Stry = rand (2, 15 );
Imagestring ($ img, 5, $ strx, $ stry, substr ($ check, 781,117), ImageColorAllocate ($ img, 78 ));
$ Strx + = rand (15, 20 );
$ Stry = rand (2, 15 );
Imagestring ($ img, 5, $ strx, $ stry, substr ($ check,), ImageColorAllocate ($ img, 16, 40 ));
$ Strx + = rand (15, 20 );
$ Stry = rand (2, 15 );
Imagestring ($ img, 5, $ strx, $ stry, substr ($ check, 3, 1), ImageColorAllocate ($ img, 25, 55, 10 ));
Output Image
Header ("Content-type: image/PNG ");
ImagePNG ($ img );
Complete code
<?php $check=rand(1000,9999);Session_start(); $_SESSION["check"] = $check; $img = imagecreate(80,30); imagefill($img,0,0,ImageColorAllocate($img,255,255,255)); $y1=rand(0,30); $y2=rand(0,30); $y3=rand(0,30); $y4=rand(0,30); imageline($img,0,$y1,70, $y3,ImageColorAllocate($img,55,255,25)); imageline($img,0,$y2,70, $y4,ImageColorAllocate($img,55,55,255)); $strx=rand(3,15); $stry=rand(2,15); imagestring($img,5,$strx,$stry,substr($check,0,1),ImageColorAllocate($img,34,87,100)); $strx+=rand(15,20);$stry=rand(2,15); imagestring($img,5,$strx,$stry,substr($check,1,1),ImageColorAllocate($img,781,117,78)); $strx+=rand(15,20);$stry=rand(2,15); imagestring($img,5,$strx,$stry,substr($check,2,1),ImageColorAllocate($img,160,40,40)); $strx+=rand(15,20);$stry=rand(2,15); imagestring($img,5,$strx,$stry,substr($check,3,1),ImageColorAllocate($img,25,55,10)); Header("Content-type: image/PNG"); ImagePNG($img);
User Interface: index. php
I think everyone knows how to do this. I will give the code directly.
<! DOCTYPE html> <body> <form action = "action. php "method =" post "> <input type =" text "name =" cikle "placeholder =" Verification Code "> <br> <input type =" submit "value =" Submit "> </form> </body>The above code passes the value entered by the user to "action. php ".
Check: action. php
In this step, we need to compare the user input value with the value in the session.
Equal, the output is "correct"
Not equal. The output is "Incorrect"
<? PhpSession_start (); if ($ _ SERVER ["REQUEST_METHOD"] = "POST") {if ($ _ SESSION ["check"]! = Intval ($ _ POST ["cikle"]) {echo "Incorrect" ;}else {echo "correct ";}}Indicate the source for reprinting.
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