Simple captcha written in php

README.md

Simple captcha written in php

Usage:

if ( implode($_SESSION['captcha']) !== $_POST['captcha'] ) {
	die('Captcha incorrect')
} else {
	// captcha correct
}

captcha.php

<?php

header('Content-type: image/png');

session_start();

// image parameters
$width=120; 
$height=40;

// create image
$image = imagecreatetruecolor($width, $height); 

// colour declaration
$color_white = imagecolorallocate($image, 232, 232, 232); // 255, 255, 255
$color_gray_1 = imagecolorallocate($image, 100, 100, 100);
$color_gray_2 = imagecolorallocate($image, 50, 50, 50);

// background
imagefilledrectangle($image, 0, 0, $width, $height, $color_white); 

$font_name = __DIR__ . "/GloriaHallelujah.ttf"; // font
$font_size = 16; // font size

// characters from what will be chosen
$letters = array('a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'); 

// number of characters
$characters = 6; 

// character-dependent loop
for($i=1;$i<=$characters;$i++) { 
	$character[$i]=$letters[rand(0, count($letters)-1)]; // store random letters in a variable
}

// save the array to the sessions
$_SESSION['captcha']=$character; 

$vertical_shadow = -1; // vertical position of the shadow 
$horizontal_shadow = -1; // horizontal position of the shadow

$distance = 16; // distance between characters

// shadow creation
for($i=1;$i<=$characters;$i++) { 
	$slope_1[$i]=rand(-5 , 5); // slope
	imagettftext($image, $font_size, $slope_1[$i], ($i*$distance)+$horizontal_shadow, 30+$vertical_shadow, $color_gray_1, $font_name, $character[$i]);
}

// character creation
for($i=1;$i<=$characters;$i++) { 
	imagettftext($image, $font_size, $slope_1[$i], ($i*$distance)+1, 30, $color_gray_2, $font_name, $character[$i]);
}

// show image
imagepng($image); 

?>