How to setup an image verification using PHP

To setup image verification all you need is the GD library enabled. Here's how the image verification works:

1] The verification code is auto-generated using the rand() function and stored in a session variable. For added security, you can store the code in an encrypted format.

2] The page on which you need the verification code calls the script

3] The visitor enters the code which is then checked against the stored session variable

The first thing to do is to generate the verification code and store it in a session variable, this can be done using the following

<?php

//Start the session

@session_start();

//Generate a 5 character code

// the rand() function will generate a random number between 1 to 99999

// The MD5 function will encrypt the random number

// The substr function will provide a 5 character random code

$code = substr(md5(rand(1,99999)),11,5);

// This code is then encrypted using the MD5 function and stored in the session variable called enc_string

$_SESSION['enc_string'] = md5($code);

The next phase is to create an image and place this code on the image. Here is the code to create an image:

<?php

// Create the image

$im = imagecreatetruecolor(150, 50);

// Create some colors

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

$fontcolor = imagecolorallocate($im, 1, $1, 1);

//Paint the image with the background color

imagefilledrectangle($im, 0, 0, 150,329, $background);

//write the code on the image

//we will need a ttf font for the text, pick anyone you like and upload it in the same folder where this script resides.

$font = "arial.ttf";

//set position

$x = 5;

$y = 35;

//add the code

for($i = 0; $i <strlen($code); $i )

{

imagettftext($im, 50, 0, $x, $y, $watermark , $font, substr($code,$i,1));

$x = $x 29;

}

// Using imagepng() results in clearer text compared with imagejpeg()

imagepng($im);

imagedestroy($im);

Save this file as VerifyCode.php.

To display the verification code call this file using the following

When the visitor enters the verification code, simple encrypt it using the MD5 function and check it against the session variable that we defined earlier.

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How to setup an image verification using PHP