<?php
/**
* @file
* @version  1.0
* @author   網海浪子
* @date  2006-3-30
* @email sxf02615@163.com
* @brief    驗證碼文件類
*
*/
?>
<?php
class CCheckCodeFile
{
 //驗證碼位數
 private $mCheckCodeNum  = 4;

 //產生的驗證碼
 private $mCheckCode   = '';
 
 //驗證碼的圖片
 private $mCheckImage  = '';

 //干擾像素
 private $mDisturbColor  = '';

 //驗證碼的圖片寬度
 private $mCheckImageWidth = '80';

 //驗證碼的圖片寬度
 private $mCheckImageHeight  = '20';

 /**
 *
 * @brief  輸出頭
 *
 */
 private function OutFileHeader()
 {
  header ("Content-type: image/png");
 }

 /**
 *
 * @brief  產生驗證碼
 *
 */
 private function CreateCheckCode()
 {
  $this->mCheckCode = strtoupper(substr(md5(rand()),0,$this->mCheckCodeNum));
  return $this->mCheckCode;
 }

 /**
 *
 * @brief  產生驗證碼圖片
 *
 */
 private function CreateImage()
 {
  $this->mCheckImage = @imagecreate ($this->mCheckImageWidth,$this->mCheckImageHeight);
  imagecolorallocate ($this->mCheckImage, 200, 200, 200);
  return $this->mCheckImage;
 }

 /**
 *
 * @brief  設置圖片的干擾像素
 *
 */
 private function SetDisturbColor()
 {
  for ($i=0;$i<=128;$i++)
  {
   $this->mDisturbColor = imagecolorallocate ($this->mCheckImage, rand(0,255), rand(0,255), rand(0,255));
   imagesetpixel($this->mCheckImage,rand(2,128),rand(2,38),$this->mDisturbColor);
  }
 }

 /**
 *
 * @brief  設置驗證碼圖片的大小
 *
 * @param  $width  寬
 *
 * @param  $height 高
 *
 */
 public function SetCheckImageWH($width,$height)
 {
  if($width==''||$height=='')return false;
  $this->mCheckImageWidth  = $width;
  $this->mCheckImageHeight = $height;
  return true;
 }

 /**
 *
 * @brief  在驗證碼圖片上逐個畫上驗證碼
 *
 */
 private function WriteCheckCodeToImage()
 {
  for ($i=0;$i<=$this->mCheckCodeNum;$i++)
  {
   $bg_color = imagecolorallocate ($this->mCheckImage, rand(0,255), rand(0,128), rand(0,255));
   $x = floor($this->mCheckImageWidth/$this->mCheckCodeNum)*$i;
   $y = rand(0,$this->mCheckImageHeight-15);
   imagechar ($this->mCheckImage, 5, $x, $y, $this->mCheckCode[$i], $bg_color);
  }
 }

 /**
 *
 * @brief  輸出驗證碼圖片
 *
 */
 public function OutCheckImage()
 {
  $this ->OutFileHeader();
  $this ->CreateCheckCode();
  $this ->CreateImage();
  $this ->SetDisturbColor();
  $this ->WriteCheckCodeToImage();
  imagepng($this->mCheckImage);
  imagedestroy($this->mCheckImage);
 }
}
$c_check_code_image = new CCheckCodeFile();
//$c_check_code_image ->SetCheckImageWH(100,50);//設置顯示驗證碼圖片的尺寸
$c_check_code_image ->OutCheckImage();
?>

VeVb注：能產生隨機的英文字母和數字，不錯!