//随机因子
  private $charset = 'abcdefghjkmnprstuvwxyzABCDEFGJKMNPRSTUVWXYZ23456789';
  private $code;
  private $codeLen = 4;

  private $width = 130;
  private $heigh = 50;
  private $img;//图像

  private $font;//字体
  private $fontsize = 20;

public function __construct()
  {
    $this->font = ROOT_PATH.'/font/Chowderhead.ttf';
    $this->img = imagecreatetruecolor($this->width, $this->heigh);
  }

//生成随机码
  private function createCode()
  {
    $_len = strlen($this->charset) - 1;
    for ($i = 0; $i < $this->codeLen; $i++) {
      $this->code .= $this->charset[mt_rand(0, $_len)];
    }
  }

//生成背景
  private function createBg()
  {
$color = imagecolorallocate($this->img, mt_rand(157, 255), mt_rand(157, 255), mt_rand(157, 255));
    imagefilledrectangle($this->img, 0, $this->heigh, $this->width, 0, $color);

  }

//生成文字
  private function createFont()
  {
    $_x = $this->width / $this->codeLen;
    $_y = $this->heigh / 2;
    for ($i = 0; $i < $this->codeLen; $i++) {
      $color = imagecolorallocate($this->img, mt_rand(0, 156), mt_rand(0, 156), mt_rand(0, 156));
      imagettftext($this->img, $this->fontsize, mt_rand(-30, 30), $_x * $i + mt_rand(3, 5), $_y + mt_rand(2, 4), $color, $this->font, $this->code[$i]);
    }
  }

//生成线条，雪花
  private function createLine()
  {
    for ($i = 0; $i < 15; $i++) {
      $color = imagecolorallocate($this->img, mt_rand(0, 156), mt_rand(0, 156), mt_rand(0, 156));
      imageline($this->img, mt_rand(0, $this->width), mt_rand(0, $this->heigh), mt_rand(0, $this->width), mt_rand(0, $this->heigh), $color);
    }
    for ($i = 0; $i < 150; $i++) {
      $color = imagecolorallocate($this->img, mt_rand(200, 255), mt_rand(200, 255), mt_rand(200, 255));
      imagestring($this->img, mt_rand(1, 5), mt_rand(0, $this->width), mt_rand(0, $this->heigh), '#', $color);
    }
  }

//对外生成
  public function doImg()
  {

    $this->createBg();   //1.创建验证码背景
    $this->createCode();  //2.生成随机码
    $this->createLine();  //3.生成线条和雪花
    $this->createFont();  //4.生成文字
    $this->outPut();    //5.输出验证码图像
  }

<?php

/**
 * Created by PhpStorm.
 * User: andy
 * Date: 16-12-22
 * Time: 下午1:20
 */
class ValidateCode
{
  //随机因子
  private $charset = 'abcdefghjkmnprstuvwxyzABCDEFGJKMNPRSTUVWXYZ23456789';
  private $code;
  private $codeLen = 4;

  private $width = 130;
  private $heigh = 50;
  private $img;//图像

  private $font;//字体
  private $fontsize = 20;


  public function __construct()
  {
    $this->font = ROOT_PATH.'/font/Chowderhead.ttf';
    $this->img = imagecreatetruecolor($this->width, $this->heigh);
  }

  //生成随机码
  private function createCode()
  {
    $_len = strlen($this->charset) - 1;
    for ($i = 0; $i < $this->codeLen; $i++) {
      $this->code .= $this->charset[mt_rand(0, $_len)];
    }
  }

  //生成背景
  private function createBg()
  {

    $color = imagecolorallocate($this->img, mt_rand(157, 255), mt_rand(157, 255), mt_rand(157, 255));
    imagefilledrectangle($this->img, 0, $this->heigh, $this->width, 0, $color);

  }

  //生成文字
  private function createFont()
  {
    $_x = $this->width / $this->codeLen;
    $_y = $this->heigh / 2;
    for ($i = 0; $i < $this->codeLen; $i++) {
      $color = imagecolorallocate($this->img, mt_rand(0, 156), mt_rand(0, 156), mt_rand(0, 156));
      imagettftext($this->img, $this->fontsize, mt_rand(-30, 30), $_x * $i + mt_rand(3, 5), $_y + mt_rand(2, 4), $color, $this->font, $this->code[$i]);
    }
  }

  //生成线条，雪花
  private function createLine()
  {
    for ($i = 0; $i < 15; $i++) {
      $color = imagecolorallocate($this->img, mt_rand(0, 156), mt_rand(0, 156), mt_rand(0, 156));
      imageline($this->img, mt_rand(0, $this->width), mt_rand(0, $this->heigh), mt_rand(0, $this->width), mt_rand(0, $this->heigh), $color);
    }
    for ($i = 0; $i < 150; $i++) {
      $color = imagecolorallocate($this->img, mt_rand(200, 255), mt_rand(200, 255), mt_rand(200, 255));
      imagestring($this->img, mt_rand(1, 5), mt_rand(0, $this->width), mt_rand(0, $this->heigh), '#', $color);
    }
  }

  //输出图像
  private function outPut()
  {
    header('Content-Type: image/png');
    imagepng($this->img);
    imagedestroy($this->img);
  }

  //对外生成
  public function doImg()
  {

    $this->createBg();   //1.创建验证码背景
    $this->createCode();  //2.生成随机码
    $this->createLine();  //3.生成线条和雪花
    $this->createFont();  //4.生成文字
    $this->outPut();    //5.输出验证码图像
  }

  //获取验证码
  public function getCode()
  {
    return strtolower($this->code);
  }

}

<?php
/**
 * Created by PhpStorm.
 * User: andy
 * Date: 16-12-22
 * Time: 下午1:20
 */

define('ROOT_PATH', dirname(__FILE__));
require_once ROOT_PATH.'/includes/ValidateCode.class.php';

$_vc=new ValidateCode();
echo $_vc->doImg();

 <label>
<img src="../config/code.php" onclick="javascript:this.src='../config/code.php?tm='+Math.random();" />
</label>

<?php
/**
 * Created by PhpStorm.
 * User: andy
 * Date: 16-12-22
 * Time: 下午3:43
 */
require substr(dirname(__FILE__),0,-7).'/init.inc.php';

$_vc=new ValidateCode();
echo $_vc->doImg();
$_SESSION['ValidateCode']=$_vc->getCode();