dynamic_image_captcha.php

<?php
$wide = 1080;
$height = 50;
$handle = imagecreatetruecolor($wide, $height); #create a 640px wide 480px height image. Consider this like canvas to draw.

$green = imagecolorallocate($handle, 0, 255, 0); #assign green color
$black = imagecolorallocate($handle, 0, 0, 0); #assign black color

imagefilledrectangle($handle, 0, 0, $wide, $height, $green); #Create filled rectangle with green color. Consider like this the shape drawn over the canvas.

imagestring($handle, 5, intval($wide/2) - 30, intval($height/2) - 8, rand_string(), $black);
imagestring($handle, 5, 0, intval($height/2) + 8, date(DATE_ATOM , $_SERVER['REQUEST_TIME']), $black);

# Jpeg conversion
header("Content-type: image/jpg");
imagejpeg($handle);

imagedestroy($handle); #Destroy the image handle to free up the resource


/*Helper Section*/

function rand_string($length = 6)
{

    $master_list = array_merge(range(0, 9), range('a', 'z'), range('A', 'Z'));
    shuffle($master_list);

    $sub_element = array_slice($master_list, 0, $length);
    $to_string = implode($sub_element);

    return $to_string;
}

/*Helper Section End*/