Detailed explanation of the website verification code function code using PHP

This article mainly introduces the method of using php to implement the website verification code function. It has a very good reference value. Let’s take a look at it with the editor.

Verification code is a security measure commonly used on websites, and it is also a skill that is difficult for new webmasters to master. Here I will introduce it to you. A simple and effective verification code implementation method.

Before starting

Before we officially start, we need to turn on php's gd2 graphics library support (search for "php_gd2.dll" in php.ini, and find "; extension=php_gd2.dll" and remove the semicolon at the beginning of the sentence).

You can refer to: How to open the gd2 library of php

Core: img.php

This page generates a verification code and writes the correct value Enter Session

Randomly enter a 4-digit verification code

##$check=rand(1000,9999);

Write the generated verification code into the session

Session_start(); $_SESSION["check"] = $check;

Create A picture

$im = imagecreate(80,30);

imagefill($im,0,0,ImageColorAllocate($im, 255,255,255));

##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 in random positions

$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));

Output image

Header("Content-type: image/PNG"); ImagePNG($img);

End, the following is the complete code

         
         

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I believe everyone knows how to do it, so I will give the code directly

The above code passes the value entered by the user to "action.php"

This step is to compare the user input value with the value in the session.

If they are equal, the output will be "correct"

If they are not equal, the output will be "incorrect"

        

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