<?
function create_captcha($data = '', $img_path = '', $img_url = '', $font_path = '')
{        
    $defaults = array('word' =>'', 'img_path' =>'', 'img_url' =>'', 'img_width' =>'10', 'img_height' =>'20', 'font_path' =>'', 'expiration' => 7200);    
    
    foreach ($defaults as $key => $val)
    {
        if ( ! is_array($data))
        {
            if ( ! isset($$key) OR $$key == '')
            {
                $$key = $val;
            }
        }
        else
        {            
            $$key = ( ! isset($data[$key])) ? $val : $data[$key];
        }
    }
    
    if ($img_path == '' OR $img_url == '')
    {
        return FALSE;
    }

    if ( ! @is_dir($img_path))
    {
        return FALSE;
    }
    
    if ( ! is_really_writable($img_path))
    {
        return FALSE;
    }
            
    if ( ! extension_loaded('gd'))
    {
        return FALSE;
    }        
    
    // -----------------------------------
    // Remove old images    
    // -----------------------------------
            
    list($usec, $sec) = explode(" ", microtime());
    $now = ((float)$usec + (float)$sec);
            
    $current_dir = @opendir($img_path);
    
    while($filename = @readdir($current_dir))
    {
        if ($filename != "." and $filename != ".." and $filename != "index.html")
        {
            $name = str_replace(".jpg", "", $filename);
        
            if (($name + $expiration) < $now)
            {
                @unlink($img_path.$filename);
            }
        }
    }
    
    @closedir($current_dir);

    // -----------------------------------
    // Do we have a "word" yet?
    // -----------------------------------
    
   if ($word == '')
   {
        $pool = '23456789QWERTYUIPASDFGHJKLZXCVBNM';

        $str = '';
        for ($i = 0; $i < 4; $i++)
        {
            $str .= substr($pool, mt_rand(0, strlen($pool) -1), 1);
        }
        
        $word = $str;
   }
    
    // -----------------------------------
    // Determine angle and position    
    // -----------------------------------
    
    $length    = strlen($word);
    $angle    = ($length >= 6) ? rand(-($length-6), ($length-6)) : 0;
    $x_axis    = rand(6, (360/$length)-16);            
    $y_axis = ($angle >= 0 ) ? rand($img_height, $img_width) : rand(6, $img_height);
    
    // -----------------------------------
    // Create image
    // -----------------------------------
            
    // PHP.net recommends imagecreatetruecolor(), but it isn't always available
    if (function_exists('imagecreatetruecolor'))
    {
        $im = imagecreatetruecolor($img_width, $img_height);
    }
    else
    {
        $im = imagecreate($img_width, $img_height);
    }
            
    // -----------------------------------
    //  Assign colors
    // -----------------------------------
    
    $bg_color        = imagecolorallocate ($im, 255, 255, 255);
    $border_color    = imagecolorallocate ($im, 255, 255, 255);
    $text_color        = imagecolorallocate ($im, 20, 5, 209);
    $grid_color        = imagecolorallocate($im, 255, 255, 255);
    $shadow_color    = imagecolorallocate($im, 255, 255, 255);

    // -----------------------------------
    //  Create the rectangle
    // -----------------------------------
    
    ImageFilledRectangle($im, 0, 0, $img_width, $img_height, $bg_color);
    
    // -----------------------------------
    //  Create the spiral pattern
    // -----------------------------------
    
    $theta        = 1;
    $thetac        = 1;
    $radius        = 1;
    $circles    = 1;
    $points        = 1;

    for ($i = 0; $i < ($circles * $points) - 1; $i++)
    {
        $theta = $theta + $thetac;
        $rad = $radius * ($i / $points );
        $x = ($rad * cos($theta)) + $x_axis;
        $y = ($rad * sin($theta)) + $y_axis;
        $theta = $theta + $thetac;
        $rad1 = $radius * (($i + 1) / $points);
        $x1 = ($rad1 * cos($theta)) + $x_axis;
        $y1 = ($rad1 * sin($theta )) + $y_axis;
        imageline($im, $x, $y, $x1, $y1, $grid_color);
        $theta = $theta - $thetac;
    }

    // -----------------------------------
    //  Write the text
    // -----------------------------------
    
    $use_font = ($font_path != '' AND file_exists($font_path) AND function_exists('imagettftext')) ? TRUE : FALSE;
    
    if ($use_font == FALSE)
    {
        $font_size = 6;
        $x = 0;
        $y = 0;
    }
    else
    {
        $font_size    = 14;
        $x = 0;
        $y = 0;
    }

    for ($i = 0; $i < strlen($word); $i++)
    {
        if ($use_font == FALSE)
        {
            $y = rand(0 , $img_height/8);
            imagestring($im, $font_size, $x, $y, substr($word, $i, 1), $text_color);
            $x += ($font_size*14);
        }
        else
        {        
            $y = 20;
            
            imagettftext($im, $font_size, $angle, $x, $y, $text_color, $font_path, substr($word, $i, 1));
            $x += $font_size;
        }
    }
    

    // -----------------------------------
    //  Create the border
    // -----------------------------------

    imagerectangle($im, 0, 0, $img_width-1, $img_height-1, $border_color);        

    // -----------------------------------
    //  Generate the image
    // -----------------------------------
    
    $img_name = $now.'.jpg';

    ImageJPEG($im, $img_path.$img_name);
    
    $img = "<img src=\"$img_url$img_name\" width=\"$img_width\" height=\"$img_height\" style=\"border:0;\" alt=\" \" />";
    
    ImageDestroy($im);
        
    return array('word' => $word, 'time' => $now, 'image' => $img);
}
?>