<?php
/**
 * Project:     Securimage: A PHP class for creating and managing form CAPTCHA images<br />
 * File:        securimage.php<br />
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or any later version.<br /><br />
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.<br /><br />
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA<br /><br />
 *
 * Any modifications to the library should be indicated clearly in the source code
 * to inform users that the changes are not a part of the original software.<br /><br />
 *
 * If you found this script useful, please take a quick moment to rate it.<br />
 * http://www.hotscripts.com/rate/49400.html  Thanks.
 *
 * @link http://www.phpcaptcha.org Securimage PHP CAPTCHA
 * @link http://www.phpcaptcha.org/latest.zip Download Latest Version
 * @link http://www.phpcaptcha.org/Securimage_Docs/ Online Documentation
 * @copyright 2007 Drew Phillips
 * @author drew010 <drew@drew-phillips.com>
 * @version 1.0.3.1 (March 24, 2008)
 * @package Securimage
 *
 */
/**
  ChangeLog

  1.0.3.1
  - Error reading from wordlist in some cases caused words to be cut off 1 letter short

  1.0.3
  - Removed shadow_text from code which could cause an undefined property error due to removal from previous version

  1.0.2
  - Audible CAPTCHA Code wav files
  - Create codes from a word list instead of random strings

  1.0
  - Added the ability to use a selected character set, rather than a-z0-9 only.
  - Added the multi-color text option to use different colors for each letter.
  - Switched to automatic session handling instead of using files for code storage
  - Added GD Font support if ttf support is not available.  Can use internal GD fonts or load new ones.
  - Added the ability to set line thickness
  - Added option for drawing arced lines over letters
  - Added ability to choose image type for output

 */
/**
 * Output images in JPEG format
 */
define('SI_IMAGE_JPEG', 1);
/**
 * Output images in PNG format
 */
define('SI_IMAGE_PNG', 2);
/**
 * Output images in GIF format
 * Must have GD >= 2.0.28!
 */
define('SI_IMAGE_GIF', 3);
define('GDFONTS', PATH_DATA . '/authcode/gdfonts/bubblebath.gdf');
define('FONT', PATH_DATA . '/authcode/font/elephant.ttf');
/**
 * Securimage CAPTCHA Class.
 *
 * @package    Securimage
 * @subpackage classes
 *
 */
 !defined('PATH_ROOT') && exit('Forbidden');
class securimage
{
	/**
	 * The desired width of the CAPTCHA image.
	 *
	 * @var int
	 */
	var $image_width = 150;
	/**
	 * The desired width of the CAPTCHA image.
	 *
	 * @var int
	 */
	var $image_height = 50;
	/**
	 * The image format for output.<br />
	 * Valid options: SI_IMAGE_PNG, SI_IMAGE_JPG, SI_IMAGE_GIF
	 *
	 * @var int
	 */
	var $image_type = SI_IMAGE_PNG;
	/**
	 * The length of the code to generate.
	 *
	 * @var int
	 */
	var $code_length = 4;
	/**
	 * The character set for individual characters in the image.<br />
	 * Letters are converted to uppercase.<br />
	 * The font must support the letters or there may be problematic substitutions.
	 *
	 * @var string
	 */
	var $charset = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';
	//var $charset = '0123456789';
	/**
	 * Create codes using this word list
	 *
	 * @var string  The path to the word list to use for creating CAPTCHA codes
	 */
	var $wordlist_file = '../words/words.txt';
	/**
	 * True to use a word list file instead of a random code
	 *
	 * @var bool
	 */
	var $use_wordlist = true;
	/**
	 * Whether to use a GD font instead of a TTF font.<br />
	 * TTF offers more support and options, but use this if your PHP doesn't support TTF.<br />
	 *
	 * @var boolean
	 */
	var $use_gd_font = false;
	/**
	 * The GD font to use.<br />
	 * Internal gd fonts can be loaded by their number.<br />
	 * Alternatively, a file path can be given and the font will be loaded from file.
	 *
	 * @var mixed
	 */
	var $gd_font_file = GDFONTS;
	/**
	 * The approximate size of the font in pixels.<br />
	 * This does not control the size of the font because that is determined by the GD font itself.<br />
	 * This is used to aid the calculations of positioning used by this class.<br />
	 *
	 * @var int
	 */
	var $gd_font_size = 20;
	// Note: These font options below do not apply if you set $use_gd_font to true with the exception of $text_color
	/**
	 * The path to the TTF font file to load.
	 *
	 * @var string
	 */
	var $ttf_file = FONT;
	/**
	 * The font size.<br />
	 * Depending on your version of GD, this should be specified as the pixel size (GD1) or point size (GD2)<br />
	 *
	 * @var int
	 */
	var $font_size = 25;
	/**
	 * The minimum angle in degrees, with 0 degrees being left-to-right reading text.<br />
	 * Higher values represent a counter-clockwise rotation.<br />
	 * For example, a value of 90 would result in bottom-to-top reading text.
	 *
	 * @var int
	 */
	var $text_angle_minimum = - 20;
	/**
	 * The minimum angle in degrees, with 0 degrees being left-to-right reading text.<br />
	 * Higher values represent a counter-clockwise rotation.<br />
	 * For example, a value of 90 would result in bottom-to-top reading text.
	 *
	 * @var int
	 */
	var $text_angle_maximum = 20;
	/**
	 * The X-Position on the image where letter drawing will begin.<br />
	 * This value is in pixels from the left side of the image.
	 *
	 * @var int
	 */
	var $text_x_start = 15;
	/**
	 * Letters can be spaced apart at random distances.<br />
	 * This is the minimum distance between two letters.<br />
	 * This should be <i>at least</i> as wide as a font character.<br />
	 * Small values can cause letters to be drawn over eachother.<br />
	 *
	 * @var int
	 */
	var $text_minimum_distance = 30;
	/**
	 * Letters can be spaced apart at random distances.<br />
	 * This is the maximum distance between two letters.<br />
	 * This should be <i>at least</i> as wide as a font character.<br />
	 * Small values can cause letters to be drawn over eachother.<br />
	 *
	 * @var int
	 */
	var $text_maximum_distance = 33;
	/**
	 * The background color for the image.<br />
	 * This should be specified in HTML hex format.<br />
	 * Make sure to include the preceding # sign!
	 *
	 * @var string
	 */
	var $image_bg_color = "#e3daed";
	/**
	 * The text color to use for drawing characters.<br />
	 * This value is ignored if $use_multi_text is set to true.<br />
	 * Make sure this contrasts well with the background color.<br />
	 * Specify the color in HTML hex format with preceding # sign
	 *
	 * @see Securimage::$use_multi_text
	 * @var string
	 */
	var $text_color = "#ff0000";
	/**
	 * Set to true to use multiple colors for each character.
	 *
	 * @see Securimage::$multi_text_color
	 * @var boolean
	 */
	var $use_multi_text = true;
	/**
	 * String of HTML hex colors to use.<br />
	 * Separate each possible color with commas.<br />
	 * Be sure to precede each value with the # sign.
	 *
	 * @var string
	 */
	var $multi_text_color = "#0a68dd,#f65c47,#8d32fd";
	/**
	 * Set to true to make the characters appear transparent.
	 *
	 * @see Securimage::$text_transparency_percentage
	 * @var boolean
	 */
	var $use_transparent_text = true;
	/**
	 * The percentage of transparency, 0 to 100.<br />
	 * A value of 0 is completely opaque, 100 is completely transparent (invisble)
	 *
	 * @see Securimage::$use_transparent_text
	 * @var int
	 */
	var $text_transparency_percentage = 15;
	// Line options
	/**
	 * Draw vertical and horizontal lines on the image.
	 *
	 * @see Securimage::$line_color
	 * @see Securimage::$line_distance
	 * @see Securimage::$line_thickness
	 * @see Securimage::$draw_lines_over_text
	 * @var boolean
	 */
	var $draw_lines = true;
	/**
	 * The color of the lines drawn on the image.<br />
	 * Use HTML hex format with preceding # sign.
	 *
	 * @see Securimage::$draw_lines
	 * @var string
	 */
	var $line_color = "#80BFFF";
	/**
	 * How far apart to space the lines from eachother in pixels.
	 *
	 * @see Securimage::$draw_lines
	 * @var int
	 */
	var $line_distance = 5;
	/**
	 * How thick to draw the lines in pixels.<br />
	 * 1-3 is ideal depending on distance
	 *
	 * @see Securimage::$draw_lines
	 * @see Securimage::$line_distance
	 * @var int
	 */
	var $line_thickness = 1;
	/**
	 * Set to true to draw angled lines on the image in addition to the horizontal and vertical lines.
	 *
	 * @see Securimage::$draw_lines
	 * @var boolean
	 */
	var $draw_angled_lines = false;
	/**
	 * Draw the lines over the text.<br />
	 * If fales lines will be drawn before putting the text on the image.<br />
	 * This can make the image hard for humans to read depending on the line thickness and distance.
	 *
	 * @var boolean
	 */
	var $draw_lines_over_text = false;
	/**
	 * For added security, it is a good idea to draw arced lines over the letters to make it harder for bots to segment the letters.<br />
	 * Two arced lines will be drawn over the text on each side of the image.<br />
	 * This is currently expirimental and may be off in certain configurations.
	 *
	 * @var boolean
	 */
	var $arc_linethrough = true;
	/**
	 * The colors or color of the arced lines.<br />
	 * Use HTML hex notation with preceding # sign, and separate each value with a comma.<br />
	 * This should be similar to your font color for single color images.
	 *
	 * @var string
	 */
	var $arc_line_colors = "#8080ff";
	/**
	 * Full path to the WAV files to use to make the audio files, include trailing /.<br />
	 * Name Files  [A-Z0-9].wav
	 *
	 * @since 1.0.1
	 * @var string
	 */
	var $audio_path = './audio/';
	//END USER CONFIGURATION
	//There should be no need to edit below unless you really know what you are doing.
	/**
	 * The gd image resource.
	 *
	 * @access private
	 * @var resource
	 */
	var $im;
	/**
	 * The background image resource
	 *
	 * @access private
	 * @var resource
	 */
	var $bgimg;
	/**
	 * The code generated by the script
	 *
	 * @access private
	 * @var string
	 */
	var $code;
	/**
	 * The code that was entered by the user
	 *
	 * @access private
	 * @var string
	 */
	var $code_entered;
	/**
	 * Whether or not the correct code was entered
	 *
	 * @access private
	 * @var boolean
	 */
	var $correct_code;

	var $session_name = "securimage_code_value";
	/**
	 * Class constructor.<br />
	 * Because the class uses sessions, this will attempt to start a session if there is no previous one.<br />
	 * If you do not start a session before calling the class, the constructor must be called before any
	 * output is sent to the browser.
	 *
	 * <code>
	 *   $securimage = new Securimage();
	 * </code>
	 *
	 */
	function __construct ()
	{
		if (session_id() == '') { // no session has been started yet, which is needed for validation
			session_start();
		}
	}
	/**
	 * Generate a code and output the image to the browser.
	 *
	 * <code>
	 *   
	 *   include 'securimage.php';
	 *   $securimage = new Securimage();
	 *   $securimage->show('bg.jpg');
	 *   
	 * </code>
	 *
	 * @param string $background_image  The path to an image to use as the background for the CAPTCHA
	 */
	function show ($background_image = "")
	{
		if ($background_image != "" && is_readable($background_image)) {
			$this->bgimg = $background_image;
		}
		$this->doImage();
	}
	/**
	 * Validate the code entered by the user.
	 *
	 * <code>
	 *   $code = $_POST['code'];
	 *   if ($securimage->check($code) == false) {
	 *     die("Sorry, the code entered did not match.");
	 *   } else {
	 *     $valid = true;
	 *   }
	 * </code>
	 * @param string $code  The code the user entered
	 * @return boolean  true if the code was correct, false if not
	 */
	function check ($code)
	{
		$this->code_entered = $code;
		$this->validate();
		return $this->correct_code;
	}
	/**
	 * Generate and output the image
	 *
	 * @access private
	 *
	 */
	function doImage ()
	{
		if ($this->use_transparent_text == true || $this->bgimg != "") {
			$this->im = imagecreatetruecolor($this->image_width, $this->image_height);
			$bgcolor = imagecolorallocate($this->im, hexdec(substr($this->image_bg_color, 1, 2)), hexdec(substr($this->image_bg_color, 3, 2)), hexdec(substr($this->image_bg_color, 5, 2)));
			imagefilledrectangle($this->im, 0, 0, imagesx($this->im), imagesy($this->im), $bgcolor);
		} else { //no transparency
			$this->im = imagecreate($this->image_width, $this->image_height);
			$bgcolor = imagecolorallocate($this->im, hexdec(substr($this->image_bg_color, 1, 2)), hexdec(substr($this->image_bg_color, 3, 2)), hexdec(substr($this->image_bg_color, 5, 2)));
		}
		if ($this->bgimg != "") {
			$this->setBackground();
		}
		$this->createCode();
		if (! $this->draw_lines_over_text && $this->draw_lines)
			$this->drawLines();
		$this->drawWord();
		if ($this->arc_linethrough == true)
			$this->arcLines();
		if ($this->draw_lines_over_text && $this->draw_lines)
			$this->drawLines();
		$this->output();
	}
	/**
	 * Set the background of the CAPTCHA image
	 *
	 * @access private
	 *
	 */
	function setBackground ()
	{
		$dat = @getimagesize($this->bgimg);
		if ($dat == false) {
			return;
		}
		switch ($dat[2]) {
			case 1:
				$newim = @imagecreatefromgif($this->bgimg);
				break;
			case 2:
				$newim = @imagecreatefromjpeg($this->bgimg);
				break;
			case 3:
				$newim = @imagecreatefrompng($this->bgimg);
				break;
			case 15:
				$newim = @imagecreatefromwbmp($this->bgimg);
				break;
			case 16:
				$newim = @imagecreatefromxbm($this->bgimg);
				break;
			default:
				return;
		}
		if (! $newim)
			return;
		imagecopy($this->im, $newim, 0, 0, 0, 0, $this->image_width, $this->image_height);
	}
	/**
	 * Draw arced lines over the text
	 *
	 * @access private
	 *
	 */
	function arcLines ()
	{
		$colors = explode(',', $this->arc_line_colors);
		imagesetthickness($this->im, 3);
		$color = $colors[rand(0, sizeof($colors) - 1)];
		$linecolor = imagecolorallocate($this->im, hexdec(substr($color, 1, 2)), hexdec(substr($color, 3, 2)), hexdec(substr($color, 5, 2)));
		$xpos = $this->text_x_start + ($this->font_size * 2) + rand(- 5, 5);
		$width = $this->image_width / 2.66 + rand(3, 10);
		$height = $this->font_size * 2.14 - rand(3, 10);
		if (rand(0, 100) % 2 == 0) {
			$start = rand(0, 66);
			$ypos = $this->image_height / 2 - rand(5, 15);
			$xpos += rand(5, 15);
		} else {
			$start = rand(180, 246);
			$ypos = $this->image_height / 2 + rand(5, 15);
		}
		$end = $start + rand(75, 110);
		imagearc($this->im, $xpos, $ypos, $width, $height, $start, $end, $linecolor);
		$color = $colors[rand(0, sizeof($colors) - 1)];
		$linecolor = imagecolorallocate($this->im, hexdec(substr($color, 1, 2)), hexdec(substr($color, 3, 2)), hexdec(substr($color, 5, 2)));
		if (rand(1, 75) % 2 == 0) {
			$start = rand(45, 111);
			$ypos = $this->image_height / 2 - rand(5, 15);
			$xpos += rand(5, 15);
		} else {
			$start = rand(200, 250);
			$ypos = $this->image_height / 2 + rand(5, 15);
		}
		$end = $start + rand(75, 100);
		imagearc($this->im, $this->image_width * .75, $ypos, $width, $height, $start, $end, $linecolor);
	}
	/**
	 * Draw lines on the image
	 *
	 * @access private
	 *
	 */
	function drawLines ()
	{
		$linecolor = imagecolorallocate($this->im, hexdec(substr($this->line_color, 1, 2)), hexdec(substr($this->line_color, 3, 2)), hexdec(substr($this->line_color, 5, 2)));
		imagesetthickness($this->im, $this->line_thickness);
		//vertical lines
		for ($x = 1; $x < $this->image_width; $x += $this->line_distance) {
			imageline($this->im, $x, 0, $x, $this->image_height, $linecolor);
		}
		//horizontal lines
		for ($y = 11; $y < $this->image_height; $y += $this->line_distance) {
			imageline($this->im, 0, $y, $this->image_width, $y, $linecolor);
		}
		if ($this->draw_angled_lines == true) {
			for ($x = - ($this->image_height); $x < $this->image_width; $x += $this->line_distance) {
				imageline($this->im, $x, 0, $x + $this->image_height, $this->image_height, $linecolor);
			}
			for ($x = $this->image_width + $this->image_height; $x > 0; $x -= $this->line_distance) {
				imageline($this->im, $x, 0, $x - $this->image_height, $this->image_height, $linecolor);
			}
		}
	}
	/**
	 * Draw the CAPTCHA code over the image
	 *
	 * @access private
	 *
	 */
	function drawWord ()
	{
		if ($this->use_gd_font == true) {
			if (! is_int($this->gd_font_file)) { //is a file name
				$font = @imageloadfont($this->gd_font_file);
				if ($font == false) {
					trigger_error("Failed to load GD Font file {$this->gd_font_file} ", E_USER_WARNING);
					return;
				}
			} else { //gd font identifier
				$font = $this->gd_font_file;
			}
			$color = imagecolorallocate($this->im, hexdec(substr($this->text_color, 1, 2)), hexdec(substr($this->text_color, 3, 2)), hexdec(substr($this->text_color, 5, 2)));
			imagestring($this->im, $font, $this->text_x_start, ($this->image_height / 2) - ($this->gd_font_size / 2), $this->code, $color);
		} else { //ttf font
			if ($this->use_transparent_text == true) {
				$alpha = intval($this->text_transparency_percentage / 100 * 127);
				$font_color = imagecolorallocatealpha($this->im, hexdec(substr($this->text_color, 1, 2)), hexdec(substr($this->text_color, 3, 2)), hexdec(substr($this->text_color, 5, 2)), $alpha);
			} else { //no transparency
				$font_color = imagecolorallocate($this->im, hexdec(substr($this->text_color, 1, 2)), hexdec(substr($this->text_color, 3, 2)), hexdec(substr($this->text_color, 5, 2)));
			}
			$x = $this->text_x_start;
			$strlen = strlen($this->code);
			$y_min = ($this->image_height / 2) + ($this->font_size / 2) - 2;
			$y_max = ($this->image_height / 2) + ($this->font_size / 2) + 2;
			$colors = explode(',', $this->multi_text_color);
			for ($i = 0; $i < $strlen; ++ $i) {
				$angle = rand($this->text_angle_minimum, $this->text_angle_maximum);
				$y = rand($y_min, $y_max);
				if ($this->use_multi_text == true) {
					$idx = rand(0, sizeof($colors) - 1);
					$r = substr($colors[$idx], 1, 2);
					$g = substr($colors[$idx], 3, 2);
					$b = substr($colors[$idx], 5, 2);
					if ($this->use_transparent_text == true) {
						$font_color = imagecolorallocatealpha($this->im, "0x$r", "0x$g", "0x$b", $alpha);
					} else {
						$font_color = imagecolorallocate($this->im, "0x$r", "0x$g", "0x$b");
					}
				}
				@imagettftext($this->im, $this->font_size, $angle, $x, $y, $font_color, $this->ttf_file, $this->code{$i});
				$x += rand($this->text_minimum_distance, $this->text_maximum_distance);
			} //for loop
		} //else ttf font
	} //function
	/**
	 * Create a code and save to the session
	 *
	 * @since 1.0.1
	 *
	 */
	function createCode ()
	{
		$this->code = false;
		if ($this->use_wordlist && is_readable($this->wordlist_file)) {
			$this->code = $this->readCodeFromFile();
		}
		if ($this->code == false) {
			$this->code = $this->generateCode($this->code_length);
		}
		$this->saveData();
	}
	/**
	 * Generate a code
	 *
	 * @access private
	 * @param int $len  The code length
	 * @return string
	 */
	function generateCode ($len)
	{
		$code = '';
		for ($i = 1, $cslen = strlen($this->charset); $i <= $len; ++ $i) {
			$code .= strtoupper($this->charset{rand(0, $cslen - 1)});
		}
		return $code;
	}
	/**
	 * Reads a word list file to get a code
	 *
	 * @access private
	 * @since 1.0.2
	 * @return mixed  false on failure, a word on success
	 */
	function readCodeFromFile ()
	{
		$fp = @fopen($this->wordlist_file, 'rb');
		if (! $fp)
			return false;
		$fsize = filesize($this->wordlist_file);
		if ($fsize < 32)
			return false; // too small of a list to be effective
		if ($fsize < 128) {
			$max = $fsize; // still pretty small but changes the range of seeking
		} else {
			$max = 128;
		}
		fseek($fp, rand(0, $fsize - $max), SEEK_SET);
		$data = fread($fp, 128); // read a random 128 bytes from file
		fclose($fp);
		$data = preg_replace("/\r?\n/", "\n", $data);
		$start = strpos($data, "\n", rand(0, 100)) + 1; // random start position
		$end = strpos($data, "\n", $start); // find end of word
		return strtolower(substr($data, $start, $end - $start)); // return substring in 128 bytes
	}
	/**
	 * Output image to the browser
	 *
	 * @access private
	 *
	 */
	function output ()
	{
		header("Expires: Sun, 1 Jan 2000 12:00:00 GMT");
		header("Last-Modified: " . gmdate("D, d M Y H:i:s") . "GMT");
		header("Cache-Control: no-store, no-cache, must-revalidate");
		header("Cache-Control: post-check=0, pre-check=0", false);
		header("Pragma: no-cache");
		switch ($this->image_type) {
			case SI_IMAGE_JPEG:
				header("Content-Type: image/jpeg");
				imagejpeg($this->im, null, 90);
				break;
			case SI_IMAGE_GIF:
				header("Content-Type: image/gif");
				imagegif($this->im);
				break;
			default:
				header("Content-Type: image/png");
				imagepng($this->im);
				break;
		}
		imagedestroy($this->im);
	}
	/**
	 * Get WAV file data of the spoken code.<br />
	 * This is appropriate for output to the browser as audio/x-wav
	 *
	 * @since 1.0.1
	 * @return string  WAV data
	 *
	 */
	function getAudibleCode ()
	{
		$letters = array();
		$code = $this->getCode();
		if ($code == '') {
			$this->createCode();
			$code = $this->getCode();
		}
		for ($i = 0; $i < strlen($code); ++ $i) {
			$letters[] = $code{$i};
		}
		return $this->generateWAV($letters);
	}
	/**
	 * Save the code in the session
	 *
	 * @access private
	 *
	 */
	function saveData ()
	{
		$_SESSION["{$this->session_name}"] = strtolower($this->code);
	}
	/**
	 * Validate the code to the user code
	 *
	 * @access private
	 *
	 */
	function validate ()
	{
		if (isset($_SESSION["{$this->session_name}"]) && ! empty($_SESSION["{$this->session_name}"])) {
			if ($_SESSION["{$this->session_name}"] == strtolower(trim($this->code_entered))) {
				$this->correct_code = true;
				$_SESSION["{$this->session_name}"] = '';
			} else {
				$this->correct_code = false;
			}
		} else {
			$this->correct_code = false;
		}
	}
	/**
	 * Get the captcha code
	 *
	 * @since 1.0.1
	 * @return string
	 */
	function getCode ()
	{
		if (isset($_SESSION["{$this->session_name}"]) && ! empty($_SESSION["{$this->session_name}"])) {
			return $_SESSION["{$this->session_name}"];
		} else {
			return '';
		}
	}
	/**
	 * Check if the user entered code was correct
	 *
	 * @access private
	 * @return boolean
	 */
	function checkCode ()
	{
		return $this->correct_code;
	}
	/**
	 * Generate a wav file by concatenating individual files
	 * @since 1.0.1
	 * @access private
	 * @param array $letters  Array of letters to build a file from
	 * @return string  WAV file data
	 */
	function generateWAV ($letters)
	{
		$first = true; // use first file to write the header...
		$data_len = 0;
		$files = array();
		$out_data = '';
		foreach ($letters as $letter) {
			$filename = $this->audio_path . strtoupper($letter) . '.wav';
			$fp = fopen($filename, 'rb');
			$file = array();
			$data = fread($fp, filesize($filename)); // read file in
			$header = substr($data, 0, 36);
			$body = substr($data, 44);
			$data = unpack('NChunkID/VChunkSize/NFormat/NSubChunk1ID/VSubChunk1Size/vAudioFormat/vNumChannels/VSampleRate/VByteRate/vBlockAlign/vBitsPerSample', $header);
			$file['sub_chunk1_id'] = $data['SubChunk1ID'];
			$file['bits_per_sample'] = $data['BitsPerSample'];
			$file['channels'] = $data['NumChannels'];
			$file['format'] = $data['AudioFormat'];
			$file['sample_rate'] = $data['SampleRate'];
			$file['size'] = $data['ChunkSize'] + 8;
			$file['data'] = $body;
			if (($p = strpos($file['data'], 'LIST')) !== false) {
				// If the LIST data is not at the end of the file, this will probably break your sound file
				$info = substr($file['data'], $p + 4, 8);
				$data = unpack('Vlength/Vjunk', $info);
				$file['data'] = substr($file['data'], 0, $p);
				$file['size'] = $file['size'] - (strlen($file['data']) - $p);
			}
			$files[] = $file;
			$data = null;
			$header = null;
			$body = null;
			$data_len += strlen($file['data']);
			fclose($fp);
		}
		$out_data = '';
		for ($i = 0; $i < sizeof($files); ++ $i) {
			if ($i == 0) { // output header
				$out_data .= pack('C4VC8', ord('R'), ord('I'), ord('F'), ord('F'), $data_len + 36, ord('W'), ord('A'), ord('V'), ord('E'), ord('f'), ord('m'), ord('t'), ord(' '));
				$out_data .= pack('VvvVVvv', 16, $files[$i]['format'], $files[$i]['channels'], $files[$i]['sample_rate'], $files[$i]['sample_rate'] * (($files[$i]['bits_per_sample'] * $files[$i]['channels']) / 8), ($files[$i]['bits_per_sample'] * $files[$i]['channels']) / 8, $files[$i]['bits_per_sample']);
				$out_data .= pack('C4', ord('d'), ord('a'), ord('t'), ord('a'));
				$out_data .= pack('V', $data_len);
			}
			$out_data .= $files[$i]['data'];
		}
		return $out_data;
	}
} /* class Securimage */
