diff --git a/application/controllers/Captcha.php b/application/controllers/Captcha.php
index 20695c94..f18e3e84 100644
--- a/application/controllers/Captcha.php
+++ b/application/controllers/Captcha.php
@@ -17,15 +17,24 @@
  * @package Controllers
  */
 class Captcha extends EA_Controller {
+    /**
+     * Class Constructor
+     */
+    public function __construct()
+    {
+        parent::__construct();
+
+        $this->load->library('captcha_builder');
+    }
+
     /**
      * Make a request to this method to get a captcha image.
      */
     public function index()
     {
         header('Content-type: image/jpeg');
-        $builder = new Gregwar\Captcha\CaptchaBuilder;
-        $builder->build();
-        $this->session->set_userdata('captcha_phrase', $builder->getPhrase());
-        $builder->output();
+        $this->captcha_builder->build();
+        $this->session->set_userdata('captcha_phrase', $this->captcha_builder->getPhrase());
+        $this->captcha_builder->output();
     }
 }
diff --git a/application/libraries/Captcha_builder.php b/application/libraries/Captcha_builder.php
new file mode 100644
index 00000000..cc7a6893
--- /dev/null
+++ b/application/libraries/Captcha_builder.php
@@ -0,0 +1,806 @@
+<?php defined('BASEPATH') or exit('No direct script access allowed');
+
+/* ----------------------------------------------------------------------------
+ * Easy!Appointments - Open Source Web Scheduler
+ *
+ * @package     EasyAppointments
+ * @author      A.Tselegidis <alextselegidis@gmail.com>
+ * @copyright   Copyright (c) 2013 - 2020, Alex Tselegidis
+ * @license     http://opensource.org/licenses/GPL-3.0 - GPLv3
+ * @link        http://easyappointments.org
+ * @since       v1.4.3
+ * ---------------------------------------------------------------------------- */
+
+use Gregwar\Captcha\PhraseBuilder;
+use Gregwar\Captcha\PhraseBuilderInterface;
+
+/**
+ * Class Captcha_builder
+ *
+ * This class replaces the Gregwar\Captcha\CaptchaBuilder so that it becomes PHP 8.1 compatible.
+ */
+class Captcha_builder {
+    /**
+     * @var array
+     */
+    protected $fingerprint = [];
+
+    /**
+     * @var bool
+     */
+    protected $useFingerprint = FALSE;
+
+    /**
+     * @var array
+     */
+    protected $textColor = [];
+
+    /**
+     * @var array
+     */
+    protected $lineColor = NULL;
+
+    /**
+     * @var array
+     */
+    protected $backgroundColor = NULL;
+
+    /**
+     * @var array
+     */
+    protected $backgroundImages = [];
+
+    /**
+     * @var resource
+     */
+    protected $contents = NULL;
+
+    /**
+     * @var string
+     */
+    protected $phrase = NULL;
+
+    /**
+     * @var PhraseBuilderInterface
+     */
+    protected $builder;
+
+    /**
+     * @var bool
+     */
+    protected $distortion = TRUE;
+
+    /**
+     * The maximum number of lines to draw in front of
+     * the image. null - use default algorithm
+     */
+    protected $maxFrontLines = NULL;
+
+    /**
+     * The maximum number of lines to draw behind
+     * the image. null - use default algorithm
+     */
+    protected $maxBehindLines = NULL;
+
+    /**
+     * The maximum angle of char
+     */
+    protected $maxAngle = 8;
+
+    /**
+     * The maximum offset of char
+     */
+    protected $maxOffset = 5;
+
+    /**
+     * Is the interpolation enabled ?
+     *
+     * @var bool
+     */
+    protected $interpolation = TRUE;
+
+    /**
+     * Ignore all effects
+     *
+     * @var bool
+     */
+    protected $ignoreAllEffects = FALSE;
+
+    /**
+     * Allowed image types for the background images
+     *
+     * @var array
+     */
+    protected $allowedBackgroundImageTypes = ['image/png', 'image/jpeg', 'image/gif'];
+
+    /**
+     * The image contents
+     */
+    public function getContents()
+    {
+        return $this->contents;
+    }
+
+    /**
+     * Enable/Disables the interpolation
+     *
+     * @param $interpolate bool  True to enable, false to disable
+     *
+     * @return Captcha_builder
+     */
+    public function setInterpolation($interpolate = TRUE)
+    {
+        $this->interpolation = $interpolate;
+
+        return $this;
+    }
+
+    /**
+     * Temporary dir, for OCR check
+     */
+    public $tempDir = 'temp/';
+
+    public function __construct($phrase = NULL, PhraseBuilderInterface $builder = NULL)
+    {
+        if ($builder === NULL)
+        {
+            $this->builder = new PhraseBuilder;
+        }
+        else
+        {
+            $this->builder = $builder;
+        }
+
+        $this->phrase = is_string($phrase) ? $phrase : $this->builder->build($phrase);
+    }
+
+    /**
+     * Setting the phrase
+     */
+    public function setPhrase($phrase)
+    {
+        $this->phrase = (string)$phrase;
+    }
+
+    /**
+     * Enables/disable distortion
+     */
+    public function setDistortion($distortion)
+    {
+        $this->distortion = (bool)$distortion;
+
+        return $this;
+    }
+
+    public function setMaxBehindLines($maxBehindLines)
+    {
+        $this->maxBehindLines = $maxBehindLines;
+
+        return $this;
+    }
+
+    public function setMaxFrontLines($maxFrontLines)
+    {
+        $this->maxFrontLines = $maxFrontLines;
+
+        return $this;
+    }
+
+    public function setMaxAngle($maxAngle)
+    {
+        $this->maxAngle = $maxAngle;
+
+        return $this;
+    }
+
+    public function setMaxOffset($maxOffset)
+    {
+        $this->maxOffset = $maxOffset;
+
+        return $this;
+    }
+
+    /**
+     * Gets the captcha phrase
+     */
+    public function getPhrase()
+    {
+        return $this->phrase;
+    }
+
+    /**
+     * Returns true if the given phrase is good
+     */
+    public function testPhrase($phrase)
+    {
+        return ($this->builder->niceize($phrase) == $this->builder->niceize($this->getPhrase()));
+    }
+
+    /**
+     * Instantiation
+     */
+    public static function create($phrase = NULL)
+    {
+        return new self($phrase);
+    }
+
+    /**
+     * Sets the text color to use
+     */
+    public function setTextColor($r, $g, $b)
+    {
+        $this->textColor = [$r, $g, $b];
+
+        return $this;
+    }
+
+    /**
+     * Sets the background color to use
+     */
+    public function setBackgroundColor($r, $g, $b)
+    {
+        $this->backgroundColor = [$r, $g, $b];
+
+        return $this;
+    }
+
+    public function setLineColor($r, $g, $b)
+    {
+        $this->lineColor = [$r, $g, $b];
+
+        return $this;
+    }
+
+    /**
+     * Sets the ignoreAllEffects value
+     *
+     * @param bool $ignoreAllEffects
+     * @return Captcha_builder
+     */
+    public function setIgnoreAllEffects($ignoreAllEffects)
+    {
+        $this->ignoreAllEffects = $ignoreAllEffects;
+
+        return $this;
+    }
+
+    /**
+     * Sets the list of background images to use (one image is randomly selected)
+     */
+    public function setBackgroundImages(array $backgroundImages)
+    {
+        $this->backgroundImages = $backgroundImages;
+
+        return $this;
+    }
+
+    /**
+     * Draw lines over the image
+     */
+    protected function drawLine($image, $width, $height, $tcol = NULL)
+    {
+        if ($this->lineColor === NULL)
+        {
+            $red = $this->rand(100, 255);
+            $green = $this->rand(100, 255);
+            $blue = $this->rand(100, 255);
+        }
+        else
+        {
+            $red = $this->lineColor[0];
+            $green = $this->lineColor[1];
+            $blue = $this->lineColor[2];
+        }
+
+        if ($tcol === NULL)
+        {
+            $tcol = imagecolorallocate($image, $red, $green, $blue);
+        }
+
+        if ($this->rand(0, 1))
+        { // Horizontal
+            $Xa = $this->rand(0, $width / 2);
+            $Ya = $this->rand(0, $height);
+            $Xb = $this->rand($width / 2, $width);
+            $Yb = $this->rand(0, $height);
+        }
+        else
+        { // Vertical
+            $Xa = $this->rand(0, $width);
+            $Ya = $this->rand(0, $height / 2);
+            $Xb = $this->rand(0, $width);
+            $Yb = $this->rand($height / 2, $height);
+        }
+        imagesetthickness($image, $this->rand(1, 3));
+        imageline($image, $Xa, $Ya, $Xb, $Yb, $tcol);
+    }
+
+    /**
+     * Apply some post effects
+     */
+    protected function postEffect($image)
+    {
+        if ( ! function_exists('imagefilter'))
+        {
+            return;
+        }
+
+        if ($this->backgroundColor != NULL || $this->textColor != NULL)
+        {
+            return;
+        }
+
+        // Negate ?
+        if ($this->rand(0, 1) == 0)
+        {
+            imagefilter($image, IMG_FILTER_NEGATE);
+        }
+
+        // Edge ?
+        if ($this->rand(0, 10) == 0)
+        {
+            imagefilter($image, IMG_FILTER_EDGEDETECT);
+        }
+
+        // Contrast
+        imagefilter($image, IMG_FILTER_CONTRAST, $this->rand(-50, 10));
+
+        // Colorize
+        if ($this->rand(0, 5) == 0)
+        {
+            imagefilter($image, IMG_FILTER_COLORIZE, $this->rand(-80, 50), $this->rand(-80, 50), $this->rand(-80, 50));
+        }
+    }
+
+    /**
+     * Writes the phrase on the image
+     */
+    protected function writePhrase($image, $phrase, $font, $width, $height)
+    {
+        $length = mb_strlen($phrase);
+        if ($length === 0)
+        {
+            return \imagecolorallocate($image, 0, 0, 0);
+        }
+
+        // Gets the text size and start position
+        $size = (int)round($width / $length) - $this->rand(0, 3) - 1;
+        $box = \imagettfbbox($size, 0, $font, $phrase);
+        $textWidth = $box[2] - $box[0];
+        $textHeight = $box[1] - $box[7];
+        $x = (int)round(($width - $textWidth) / 2);
+        $y = (int)round(($height - $textHeight) / 2) + $size;
+
+        if ( ! $this->textColor)
+        {
+            $textColor = [$this->rand(0, 150), $this->rand(0, 150), $this->rand(0, 150)];
+        }
+        else
+        {
+            $textColor = $this->textColor;
+        }
+        $col = \imagecolorallocate($image, $textColor[0], $textColor[1], $textColor[2]);
+
+        // Write the letters one by one, with random angle
+        for ($i = 0; $i < $length; $i++)
+        {
+            $symbol = mb_substr($phrase, $i, 1);
+            $box = \imagettfbbox($size, 0, $font, $symbol);
+            $w = $box[2] - $box[0];
+            $angle = $this->rand(-$this->maxAngle, $this->maxAngle);
+            $offset = $this->rand(-$this->maxOffset, $this->maxOffset);
+            \imagettftext($image, $size, $angle, $x, $y + $offset, $col, $font, $symbol);
+            $x += $w;
+        }
+
+        return $col;
+    }
+
+    /**
+     * Try to read the code against an OCR
+     */
+    public function isOCRReadable()
+    {
+        if ( ! is_dir($this->tempDir))
+        {
+            @mkdir($this->tempDir, 0755, TRUE);
+        }
+
+        $tempj = $this->tempDir . uniqid('captcha', TRUE) . '.jpg';
+        $tempp = $this->tempDir . uniqid('captcha', TRUE) . '.pgm';
+
+        $this->save($tempj);
+        shell_exec("convert $tempj $tempp");
+        $value = trim(strtolower(shell_exec("ocrad $tempp")));
+
+        @unlink($tempj);
+        @unlink($tempp);
+
+        return $this->testPhrase($value);
+    }
+
+    /**
+     * Builds while the code is readable against an OCR
+     */
+    public function buildAgainstOCR($width = 150, $height = 40, $font = NULL, $fingerprint = NULL)
+    {
+        do
+        {
+            $this->build($width, $height, $font, $fingerprint);
+        }
+        while ($this->isOCRReadable());
+    }
+
+    /**
+     * Generate the image
+     */
+    public function build($width = 150, $height = 40, $font = NULL, $fingerprint = NULL)
+    {
+        if (NULL !== $fingerprint)
+        {
+            $this->fingerprint = $fingerprint;
+            $this->useFingerprint = TRUE;
+        }
+        else
+        {
+            $this->fingerprint = [];
+            $this->useFingerprint = FALSE;
+        }
+
+        if ($font === NULL)
+        {
+            $font = __DIR__ . '/../../vendor/gregwar/captcha/src/Gregwar/Captcha/Font/captcha' . $this->rand(0, 5) . '.ttf';
+        }
+
+        if (empty($this->backgroundImages))
+        {
+            // if background images list is not set, use a color fill as a background
+            $image = imagecreatetruecolor($width, $height);
+            if ($this->backgroundColor == NULL)
+            {
+                $bg = imagecolorallocate($image, $this->rand(200, 255), $this->rand(200, 255), $this->rand(200, 255));
+            }
+            else
+            {
+                $color = $this->backgroundColor;
+                $bg = imagecolorallocate($image, $color[0], $color[1], $color[2]);
+            }
+            $this->background = $bg;
+            imagefill($image, 0, 0, $bg);
+        }
+        else
+        {
+            // use a random background image
+            $randomBackgroundImage = $this->backgroundImages[rand(0, count($this->backgroundImages) - 1)];
+
+            $imageType = $this->validateBackgroundImage($randomBackgroundImage);
+
+            $image = $this->createBackgroundImageFromType($randomBackgroundImage, $imageType);
+        }
+
+        // Apply effects
+        if ( ! $this->ignoreAllEffects)
+        {
+            $square = $width * $height;
+            $effects = $this->rand($square / 3000, $square / 2000);
+
+            // set the maximum number of lines to draw in front of the text
+            if ($this->maxBehindLines != NULL && $this->maxBehindLines > 0)
+            {
+                $effects = min($this->maxBehindLines, $effects);
+            }
+
+            if ($this->maxBehindLines !== 0)
+            {
+                for ($e = 0; $e < $effects; $e++)
+                {
+                    $this->drawLine($image, $width, $height);
+                }
+            }
+        }
+
+        // Write CAPTCHA text
+        $color = $this->writePhrase($image, $this->phrase, $font, $width, $height);
+
+        // Apply effects
+        if ( ! $this->ignoreAllEffects)
+        {
+            $square = $width * $height;
+            $effects = $this->rand($square / 3000, $square / 2000);
+
+            // set the maximum number of lines to draw in front of the text
+            if ($this->maxFrontLines != NULL && $this->maxFrontLines > 0)
+            {
+                $effects = min($this->maxFrontLines, $effects);
+            }
+
+            if ($this->maxFrontLines !== 0)
+            {
+                for ($e = 0; $e < $effects; $e++)
+                {
+                    $this->drawLine($image, $width, $height, $color);
+                }
+            }
+        }
+
+        // Distort the image
+        if ($this->distortion && ! $this->ignoreAllEffects)
+        {
+            $image = $this->distort($image, $width, $height, $bg);
+        }
+
+        // Post effects
+        if ( ! $this->ignoreAllEffects)
+        {
+            $this->postEffect($image);
+        }
+
+        $this->contents = $image;
+
+        return $this;
+    }
+
+    /**
+     * Distorts the image
+     */
+    public function distort($image, $width, $height, $bg)
+    {
+        $contents = imagecreatetruecolor($width, $height);
+        $X = $this->rand(0, $width);
+        $Y = $this->rand(0, $height);
+        $phase = $this->rand(0, 10);
+        $scale = 1.1 + $this->rand(0, 10000) / 30000;
+        for ($x = 0; $x < $width; $x++)
+        {
+            for ($y = 0; $y < $height; $y++)
+            {
+                $Vx = $x - $X;
+                $Vy = $y - $Y;
+                $Vn = sqrt($Vx * $Vx + $Vy * $Vy);
+
+                if ($Vn != 0)
+                {
+                    $Vn2 = $Vn + 4 * sin($Vn / 30);
+                    $nX = $X + ($Vx * $Vn2 / $Vn);
+                    $nY = $Y + ($Vy * $Vn2 / $Vn);
+                }
+                else
+                {
+                    $nX = $X;
+                    $nY = $Y;
+                }
+                $nY = $nY + $scale * sin($phase + $nX * 0.2);
+
+                if ($this->interpolation)
+                {
+                    $p = $this->interpolate(
+                        $nX - floor($nX),
+                        $nY - floor($nY),
+                        $this->getCol($image, floor($nX), floor($nY), $bg),
+                        $this->getCol($image, ceil($nX), floor($nY), $bg),
+                        $this->getCol($image, floor($nX), ceil($nY), $bg),
+                        $this->getCol($image, ceil($nX), ceil($nY), $bg)
+                    );
+                }
+                else
+                {
+                    $p = $this->getCol($image, round($nX), round($nY), $bg);
+                }
+
+                if ($p == 0)
+                {
+                    $p = $bg;
+                }
+
+                imagesetpixel($contents, $x, $y, $p);
+            }
+        }
+
+        return $contents;
+    }
+
+    /**
+     * Saves the Captcha to a jpeg file
+     */
+    public function save($filename, $quality = 90)
+    {
+        imagejpeg($this->contents, $filename, $quality);
+    }
+
+    /**
+     * Gets the image GD
+     */
+    public function getGd()
+    {
+        return $this->contents;
+    }
+
+    /**
+     * Gets the image contents
+     */
+    public function get($quality = 90)
+    {
+        ob_start();
+        $this->output($quality);
+
+        return ob_get_clean();
+    }
+
+    /**
+     * Gets the HTML inline base64
+     */
+    public function inline($quality = 90)
+    {
+        return 'data:image/jpeg;base64,' . base64_encode($this->get($quality));
+    }
+
+    /**
+     * Outputs the image
+     */
+    public function output($quality = 90)
+    {
+        imagejpeg($this->contents, NULL, $quality);
+    }
+
+    /**
+     * @return array
+     */
+    public function getFingerprint()
+    {
+        return $this->fingerprint;
+    }
+
+    /**
+     * Returns a random number or the next number in the
+     * fingerprint
+     */
+    protected function rand($min, $max)
+    {
+        if ( ! is_array($this->fingerprint))
+        {
+            $this->fingerprint = [];
+        }
+
+        if ($this->useFingerprint)
+        {
+            $value = current($this->fingerprint);
+            next($this->fingerprint);
+        }
+        else
+        {
+            $value = mt_rand((int)$min, (int)$max);
+            $this->fingerprint[] = $value;
+        }
+
+        return $value;
+    }
+
+    /**
+     * @param $x
+     * @param $y
+     * @param $nw
+     * @param $ne
+     * @param $sw
+     * @param $se
+     *
+     * @return int
+     */
+    protected function interpolate($x, $y, $nw, $ne, $sw, $se)
+    {
+        [$r0, $g0, $b0] = $this->getRGB($nw);
+        [$r1, $g1, $b1] = $this->getRGB($ne);
+        [$r2, $g2, $b2] = $this->getRGB($sw);
+        [$r3, $g3, $b3] = $this->getRGB($se);
+
+        $cx = 1.0 - $x;
+        $cy = 1.0 - $y;
+
+        $m0 = $cx * $r0 + $x * $r1;
+        $m1 = $cx * $r2 + $x * $r3;
+        $r = (int)($cy * $m0 + $y * $m1);
+
+        $m0 = $cx * $g0 + $x * $g1;
+        $m1 = $cx * $g2 + $x * $g3;
+        $g = (int)($cy * $m0 + $y * $m1);
+
+        $m0 = $cx * $b0 + $x * $b1;
+        $m1 = $cx * $b2 + $x * $b3;
+        $b = (int)($cy * $m0 + $y * $m1);
+
+        return ($r << 16) | ($g << 8) | $b;
+    }
+
+    /**
+     * @param $image
+     * @param $x
+     * @param $y
+     *
+     * @return int
+     */
+    protected function getCol($image, $x, $y, $background)
+    {
+        $L = imagesx($image);
+        $H = imagesy($image);
+        if ($x < 0 || $x >= $L || $y < 0 || $y >= $H)
+        {
+            return $background;
+        }
+
+        return imagecolorat($image, $x, $y);
+    }
+
+    /**
+     * @param $col
+     *
+     * @return array
+     */
+    protected function getRGB($col)
+    {
+        return [
+            (int)($col >> 16) & 0xff,
+            (int)($col >> 8) & 0xff,
+            (int)($col) & 0xff,
+        ];
+    }
+
+    /**
+     * Validate the background image path. Return the image type if valid
+     *
+     * @param string $backgroundImage
+     * @return string
+     * @throws Exception
+     */
+    protected function validateBackgroundImage($backgroundImage)
+    {
+        // check if file exists
+        if ( ! file_exists($backgroundImage))
+        {
+            $backgroundImageExploded = explode('/', $backgroundImage);
+            $imageFileName = count($backgroundImageExploded) > 1 ? $backgroundImageExploded[count($backgroundImageExploded) - 1] : $backgroundImage;
+
+            throw new Exception('Invalid background image: ' . $imageFileName);
+        }
+
+        // check image type
+        $finfo = finfo_open(FILEINFO_MIME_TYPE); // return mime type ala mimetype extension
+        $imageType = finfo_file($finfo, $backgroundImage);
+        finfo_close($finfo);
+
+        if ( ! in_array($imageType, $this->allowedBackgroundImageTypes))
+        {
+            throw new Exception('Invalid background image type! Allowed types are: ' . join(', ', $this->allowedBackgroundImageTypes));
+        }
+
+        return $imageType;
+    }
+
+    /**
+     * Create background image from type
+     *
+     * @param string $backgroundImage
+     * @param string $imageType
+     * @return resource
+     * @throws Exception
+     */
+    protected function createBackgroundImageFromType($backgroundImage, $imageType)
+    {
+        switch ($imageType)
+        {
+            case 'image/jpeg':
+                $image = imagecreatefromjpeg($backgroundImage);
+                break;
+            case 'image/png':
+                $image = imagecreatefrompng($backgroundImage);
+                break;
+            case 'image/gif':
+                $image = imagecreatefromgif($backgroundImage);
+                break;
+
+            default:
+                throw new Exception('Not supported file type for background image!');
+                break;
+        }
+
+        return $image;
+    }
+}