Creating a CAPTCHA with PHP

[admin]

This tutorial will show you how to create a form with Captcha.
1.Sessions in PHP are started by using the session_start() function.  Like the setcookie( ) function, the session_start( ) function must come before any HTML, including blank lines, on the page.

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session_start();
2.Imagecreatefrompng create a new image from file or URL.

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$img = imagecreatefrompng('black.png');
3.The function imagecolorallocate creates a color using RGB (red,green,blue) format.

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$white = imagecolorallocate($img, 255, 255, 255);
5.Displaying the random text on the captcha image

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$numero = rand(100, 999);
4.Check if the security code and the session value are not blank and if the input text matches the stored text.

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if(($_POST['check']) == $_SESSION['check']) {
echo 'Input O.K.';
}else{
echo 'Input Wrong';
        }
black.png


40 x 20 pixels

index.php

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<form method="POST" action="cc.php">
<img src="captchas.php"> <br>
<input type="text" size="10" name="check"> 
<input type="submit" name="submit" value="submit">
</form>
captchas.php

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<?php 
session_start(); 
//imagecreatefrompng â€” create a new image 
//from file or URL
$img = imagecreatefrompng('black.png'); 
//displaying the random text on the captcha image
$numero = rand(100, 999); 
$_SESSION['check'] = ($numero); 
//The function imagecolorallocate creates a 
//color using RGB (red,green,blue) format.
$white = imagecolorallocate($img, 255, 255, 255); 
imagestring($img, 10, 8, 3, $numero, $white); 
header ("Content-type: image/png"); 
imagepng($img); 
?>
cc.php

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<?php 
//Sessions in PHP are started by using the 
//session_start() function.  Like the setcookie( ) function, 
//the session_start( ) function must come before any HTML, 
//including blank lines, on the page.
session_start(); 
//Check if the security code and 
//the session value are not blank 
//and if the input text matches the stored text

if(($_POST['check']) == $_SESSION['check']) { 
echo 'Input O.K.';
}else{ 
echo 'Input Wrong';
        }
?>

[alex]

The imagecreate () function is used in PHP to create a new palette based image. It's two parameters are width and then height of the image to be created.

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<?php 
session_start(); 
//imagecreate -- Create a new palette based image
$img = imagecreate(40, 20);
//displaying the random text on the captcha image
$black = imagecolorallocate($img, 0, 0, 0); 
$numero = rand(100, 999);
$number = $black . $numero;
$_SESSION['check'] = ($numero); 

$white = imagecolorallocate($img, 255, 255, 255); 
imagestring($img, 10, 8, 3, $numero, $white); 
header ("Content-type: image/png"); 
imagepng($img); 
?>