不错的图片验证码

AuthCode.class.php

<? php
/* *
 * 这个类用于生成验证码图像, 同时可以对用户输入的验证码进行验证
 * 
 * @author  ♂bingo↗ [coolhpy@163.com]
 * @since   2006-6-17
  */


class  AuthCode 
{
     /* *
     * 验证码
     *  char:  字符
     *  angle: 字符偏移的角度 (-30 <= angle <= 30)
     *  color: 字符颜色
     * 
     * @var     array
     * @access  private
      */
     var   $code   =   array ();

     /* *
     * 字体信息
     *  space: 字符间隔 (px)
     *  size:  字体大小 (px)
     *  left:  第一个字符距离图像最左边的象素 (px)
     *  top:   字符距离图像最上边的象素 (px)
     *  file:  字体文件的路径
     * 
     * @var     array
     * @access  private
      */
     var   $font   =   array ();

     /* *
     * 图像信息
     *  type:   图像类型
     *  mime:   MIME 类型
     *  width:  图像的宽 (px)
     *  height: 图像高 (px)
     *  func:   创建图像的方法
     * 
     * @var     array
     * @access  private
      */
     var   $image   =   array ();

     /* *
     * 干扰信息
     *  type:    干扰类型 (false 表示不使用)
     *  density: 干扰密度
     * 
     * @var     array
     * @access  private
      */
     var   $molestation   =   array ();

     /* *
     * 背景色 (RGB)
     *  r: 红色 (0 - 255)
     *  g: 绿色 (0 - 255)
     *  b: 蓝色 (0 - 255)
     * 
     * @var     array
     * @access  private
      */
     var   $bg_color   =   array ();

     /* *
     * 默认前景色 (RGB)
     *  r: 红色 (0 - 255)
     *  g: 绿色 (0 - 255)
     *  b: 蓝色 (0 - 255)
     * 
     * @var     array
     * @access  private
      */
     var   $fg_color   =   array ();

     /* *
     * Session 变量名
     * 
     * @var     string
     * @access  private
      */
     var   $session   =   '' ;



     /* *
     * 构造函数，初始化各变量
     * 
     * @access  public
      */
     function  AuthCode() 
    {
         $this -> code  =   $this -> generateCode();
        
         $this -> molestation  =   array ( ' type ' => ' point ' ,   ' density ' => ' normal ' );
         $this -> bg_color  =   array ( ' r ' => 255 ,   ' g ' => 255 ,   ' b ' => 255 );
         $this -> fg_color  =   array ( ' r ' => 0 ,   ' g ' => 0 ,   ' b ' => 0 );
         //  image 必须在 font 之前定义
         $infomation   =   $this -> getImageType( ' png ' );
         $this -> image  =   array ( ' type ' => ' png ' ,   ' mime ' => $infomation [ ' mime ' ] ,  
                              ' func ' => $infomation [ ' func ' ] ,   ' width ' => 70 ,  
                              ' height ' => 20 );
         $this -> font  =   array ( ' space ' => 5 ,   ' size ' => 12 ,   ' left ' => 5 ,  
                             ' top ' => ( $this -> image[ ' height ' ] - 5 ) ,
                             ' file ' => ' ./arial.ttf ' );
         $this -> session  =   ' auth_code ' ;
    }

     /* *
     * 设置验证码
     * 
     * @access  public
     * @param   array   字符信息
     * characters    string  允许的字符
     * length        int     验证码长度
     * deflect       boolean 字符是否偏转
     * multicolor    boolean 字符是否彩色
     * @return  void
      */
     function  setCode( $code ) 
    {
         if  ( is_array ( $code )) 
        {
             if  ( ! isset ( $code [ ' characters ' ])  ||   ! is_string ( $code [ ' characters ' ])) 
            {
                 $code [ ' characters ' ]  =   ' A-Z,1-9 ' ;
            }
             if  ( ! ( is_integer ( $code [ ' length ' ])  ||   $code [ ' length ' ] <= 0 )) 
            {
                 $code [ ' length ' ]  =   4 ;
            }
             if  ( ! is_bool ( $code [ ' deflect ' ])) 
            {
                 $code [ ' deflect ' ]  =   true ;
            }
             if  ( ! is_bool ( $code [ ' multicolor ' ])) 
            {
                 $code [ ' multicolor ' ]  =   true ;
            }
        }  else  
        {
             $code   =   array ( ' characters ' => ' A-Z,1-9 ' ,   ' length ' => 4 ,  
                           ' deflect ' => true ,   ' multicolor ' => true );
        }

         $this -> code  =   $code ;
    }

     /* *
     * 设置 session 变量名
     * 
     * @access  public
     * @param   string  session 变量名
     * @return  void
      */
     function  setSession( $session ) 
    {
         if  ( isset ( $session )  &&   ! empty ( $session )) 
        {
             $this -> session  =   $session ;
        }  else
        {
             $this -> session  =   ' auth_code ' ;
        }
    }

     /* *
     * 设置背景色
     * 
     * @access  public
     * @param   array   RGB 颜色
     * @return  void
      */
     function  setBgColor( $color ) 
    {
         if  ( is_array ( $color )  &&   is_integer ( $color [ ' r ' ])  &&  
             is_integer ( $color [ ' g ' ])  &&   is_integer ( $color [ ' b ' ])  &&  
            ( $color [ ' r ' ]  >=   0   &&   $color [ ' r ' ]  <=   255 )  &&  
            ( $color [ ' g ' ]  >=   0   &&   $color [ ' g ' ]  <=   255 )  &&  
            ( $color [ ' b ' ]  >=   0   &&   $color [ ' b ' ]  <=   255 )) 
        {
             $this -> bg_color  =   $color ;
        }  else  
        {
             $this -> bg_color  =   array ( ' r ' => 255 , ' g ' => 255 , ' b ' => 255 );
        }

         //  设置默认的前景色, 与背景色相反
         $fg_color   =   array (
             ' r ' => 255 - $this -> bg_color[ ' r ' ] ,  
             ' g ' => 255 - $this -> bg_color[ ' g ' ] ,  
             ' b ' => 255 - $this -> bg_color[ ' b ' ]
        );
         $this -> setFgColor( $fg_color );
    }

     /* *
     * 设置干扰信息
     * 
     * @access  public
     * @param   array   干扰信息
     *  type    string  干扰类型 (选项: false, 'point', 'line')
     *  density string  干扰密度 (选项: 'normal', 'muchness', 'fewness')
     * @return  void
      */
     function  setMolestation( $molestation ) 
    {
         if  ( is_array ( $molestation )) 
        {
             if  ( ! isset ( $molestation [ ' type ' ])  ||  
                ( $molestation [ ' type ' ] != ' point '   &&  
                  $molestation [ ' type ' ] != ' line '   &&  
                  $molestation [ ' type ' ] != ' both ' )) 
            {
                 $molestation [ ' type ' ]  =   ' point ' ;
            }
             if  ( ! is_STRING ( $molestation [ ' density ' ])) 
            {
                 $molestation [ ' density ' ]  =   ' normal ' ;
            }
             $this -> molestation  =   $molestation ;
        }  else  
        {
             $this -> molestation  =   array (
                 ' type '      =>   ' point ' ,
                 ' density '   =>   ' normal '
            );
        }
    }

     /* *
     * 设置字体信息
     * 
     * @access  public
     * @param   array   字体信息
     *   space  int     字符间隔 (px)
     *   size   int     字体大小 (px)
     *   left   int     第一个字符距离图像最左边的象素 (px)
     *   top    int     字符距离图像最上边的象素 (px)
     *   file   string  字体文件的路径
     * @return  void
      */
     function  setFont( $font ) 
    {
         if  ( is_array ( $font ))
        {
             if  ( ! is_integer ( $font [ ' space ' ])  ||   $font [ ' space ' ] < 0 )
            {
                 $font [ ' space ' ]  =   5 ;
            }
             if  ( ! is_integer ( $font [ ' size ' ])  ||   $font [ ' size ' ] < 0 )
            {
                 $font [ ' size ' ]  =   12 ;
            }
             if  ( ! is_integer ( $font [ ' left ' ])  ||   $font [ ' left ' ] < 0   ||  
                 $font [ ' left ' ] > $this -> image[ ' width ' ]) 
            {
                 $font [ ' left ' ]  =   5 ;
            }
             if  ( ! is_integer ( $font [ ' top ' ])  ||   $font [ ' top ' ] < 0   ||  
                 $font [ ' top ' ] > $this -> image[ ' height ' ]) 
            {
                 $font [ ' top ' ]  =   $this -> image[ ' height ' ]  -   5 ;
            }
             if  ( ! file_exists ( $font [ ' file ' ])) 
            {
                 $font [ ' file ' ]  =   ' ./arial.ttf ' ;
            }
             $this -> font  =   $font ;
        }  else
        {
             $this -> font  =   array ( ' space ' => 5 ,   ' size ' => 5 ,   ' left ' => 5 ,  
                                 ' top ' => ( $this -> image[ ' height ' ] - 5 ) ,  
                                 ' file ' => ' ./arial.ttf ' );
        }
    }

     /* *
     * 设置图像信息
     * 
     * @access  public
     * @param   array   图像信息
     *   type   string  图像类型 (选项: 'png', 'gif', 'wbmp', 'jpg')
     *   width  int     图像宽 (px)
     *   height int     图像高 (px)
     * @return  void
      */
     function  setImage( $image ) 
    {
         if  ( is_array ( $image )) 
        {
             if  ( ! is_integer ( $image [ ' width ' ])  ||   $image [ ' width ' ]  <=   0 ) 
            {
                 $image [ ' width ' ]  =   50 ;
            }
             if  ( ! is_integer ( $image [ ' height ' ])  ||   $image [ ' height ' ]  <=   0 ) 
            {
                 $image [ ' height ' ]  =   25 ;
            }
             $this -> image  =   $image ;
             $information   =   $this -> getImageType( $image [ ' type ' ]);
             if  ( is_array ( $information )) 
            {
                 $this -> image[ ' mime ' ]  =   $information [ ' mime ' ];
                 $this -> image[ ' func ' ]  =   $information [ ' func ' ];
            }  else  
            {
                 $this -> image[ ' type ' ]  =   ' png ' ;
                 $information   =   $this -> getImageType( ' png ' );
                 $this -> image[ ' mime ' ]  =   $information [ ' mime ' ];
                 $this -> image[ ' func ' ]  =   $information [ ' func ' ];
            }
        }  else  
        {
             $information   =   $this -> getImageType( ' png ' );
             $this -> image  =   array (
                 ' type ' => ' png ' ,  
                 ' mime ' => $information [ ' mime ' ] ,  
                 ' func ' => $information [ ' func ' ] ,  
                 ' width ' => 50 ,  
                 ' height ' => 25 );
        }
    }

     /* *
     * 绘制图像
     * 
     * @access  public
     * @param   string  文件名, 留空表示输出到浏览器
     * @return  void
      */
     function  paint( $filename = '' ) 
    {
         //  创建图像
         $im   =  imagecreatetruecolor( $this -> image[ ' width ' ] ,  
                                    $this -> image[ ' height ' ]);

         //  设置图像背景
         $bg_color   =  imagecolorallocate( $im ,   $this -> bg_color[ ' r ' ] ,  
                                        $this -> bg_color[ ' g ' ] ,  
                                        $this -> bg_color[ ' b ' ]);
        imagefilledrectangle( $im ,   0 ,   0 ,   $this -> image[ ' width ' ] ,  
                              $this -> image[ ' height ' ] ,   $bg_color );

         //  生成验证码相关信息
         $code   =   $this -> generateCode();
        
         //  生成的验证码
         $the_code   =   '' ;

         //  向图像中写入字符
         $num   =   count ( $code );
         $current_left   =   $this -> font[ ' left ' ];
         $current_top    =   $this -> font[ ' top ' ];
         for  ( $i = 0 ;  $i < $num ;  $i ++ ) 
        {
             $font_color   =  imagecolorallocate( $im ,   $code [ $i ][ ' color ' ][ ' r ' ] ,  
                                              $code [ $i ][ ' color ' ][ ' g ' ] ,  
                                              $code [ $i ][ ' color ' ][ ' b ' ]);
            imagettftext( $im ,   $this -> font[ ' size ' ] ,   $code [ $i ][ ' angle ' ] ,  
                          $current_left ,   $current_top ,   $font_color ,  
                          $this -> font[ ' file ' ] ,   $code [ $i ][ ' char ' ]);
             $current_left   +=   $this -> font[ ' size ' ]  +   $this -> font[ ' space ' ];

             $the_code   .=   $code [ $i ][ ' char ' ];
        }

         //  初始化 session
        // 如果 session 未启用, 则开启它
         if  ( empty ( $_SESSION [ ' SID ' ])) @ session_start ();

         //  用 md5() 给密码加密, 写入 session
         $_SESSION [ $this -> session]  =   md5 ( $the_code );
         $_SESSION [ $this -> session . ' _none_case ' ]  =   md5 ( strtolower ( $the_code ));

         //  绘制图像干扰
         $this -> paintMolestation( $im );

         //  输出
         if  ( isset ( $filename )  &&   $filename != '' ) 
        {
             $this -> image[ ' func ' ]( $im ,   $filename . $this -> image[ ' type ' ]);
        }  else  
        {
             header ( " Cache-Control: no-cache, must-revalidate " );
             header ( " Content-type:  " . $this -> image[ ' mime ' ]);
             $this -> image[ ' func ' ]( $im );
        }
        imagedestroy( $im );
    }

     /* *
     * 验证用户输入的验证码
     * 
     * @param   string  用户输入的字符串
     * @param   boolean 是否区分大小写
     * @return  boolean 正确返回 true
      */
     function  validate( $input ,   $is_match_case = true ) 
    {
         if  ( $is_match_case ) 
        {
             return  ( strcmp ( $_SESSION [ $this -> session] ,   md5 ( $input ))  ==   0 );
        }  else  
        {
             return  ( strcmp ( $_SESSION [ $this -> session . ' _none_case ' ] ,  
                            md5 ( strtolower ( $input )))  ==   0 );
        }
    }



     /* *
     * 设置前景色
     * 
     * @access  private
     * @param   array   RGB 颜色
     * @return  void
      */
     function  setFgColor( $color ) 
    {
         if  ( is_array ( $color )  &&   is_integer ( $color [ ' r ' ])  &&  
             is_integer ( $color [ ' g ' ])  &&   is_integer ( $color [ ' b ' ])  &&  
            ( $color [ ' r ' ]  >=   0   &&   $color [ ' r ' ]  <=   255 )  &&  
            ( $color [ ' g ' ]  >=   0   &&   $color [ ' g ' ]  <=   255 )  &&  
            ( $color [ ' b ' ]  >=   0   &&   $color [ ' b ' ]  <=   255 )) 
        {
             $this -> fg_color  =   $color ;
        }  else  
        {
             $this -> fg_color  =   array ( ' r ' => 0 , ' g ' => 0 , ' b ' => 0 );
        }
    }

     /* *
     * 生成随机验证码
     * 
     * @access  private
     * @return  array   生成的验证码
      */
     function  generateCode() 
    {
         //  创建允许的字符串
         $characters   =   explode ( ' , ' ,   $this -> code[ ' characters ' ]);
         $num   =   count ( $characters );
         for  ( $i = 0 ;  $i < $num ;  $i ++ ) 
        {
             if  ( substr_count ( $characters [ $i ] ,   ' - ' )  >   0 ) 
            {
                 $character_range   =   explode ( ' - ' ,   $characters [ $i ]);
                 for  ( $j = ord ( $character_range [ 0 ]);  $j <= ord ( $character_range [ 1 ]);
                      $j ++ ) 
                {
                     $array_allow []  =   chr ( $j );
                }
            }
             else  
            {
                 $array_allow []  =   $array_allow [ $i ];
            }
        }
         $index   =   0 ;
         while  ( list ( $key ,   $val )  =   each ( $array_allow )) 
        {
             $array_allow_tmp [ $index ]  =   $val ;
             $index   ++ ;
        }
         $array_allow   =   $array_allow_tmp ;

         //  生成随机字符串
         mt_srand (( double ) microtime ()  *   1000000 );
         $code   =   array ();
         $index   =   0 ;
         $i   =   0 ;
         while  ( $i   <   $this -> code[ ' length ' ]) 
        {
             $index   =   mt_rand ( 0 ,   count ( $array_allow )  -   1 );
             $code [ $i ][ ' char ' ]  =   $array_allow [ $index ];
             if  ( $this -> code[ ' deflect ' ]) 
            {
                 $code [ $i ][ ' angle ' ]  =   mt_rand ( - 30 ,   30 );
            }  else
            {
                 $code [ $i ][ ' angle ' ]  =   0 ;
            }
             if  ( $this -> code[ ' multicolor ' ]) 
            {
                 $code [ $i ][ ' color ' ][ ' r ' ]  =   mt_rand ( 0 ,   255 );
                 $code [ $i ][ ' color ' ][ ' g ' ]  =   mt_rand ( 0 ,   255 );
                 $code [ $i ][ ' color ' ][ ' b ' ]  =   mt_rand ( 0 ,   255 );
            }  else
            {
                 $code [ $i ][ ' color ' ][ ' r ' ]  =   $this -> fg_color[ ' r ' ];
                 $code [ $i ][ ' color ' ][ ' g ' ]  =   $this -> fg_color[ ' g ' ];
                 $code [ $i ][ ' color ' ][ ' b ' ]  =   $this -> fg_color[ ' b ' ];
            }
             $i ++ ;
        }

         return   $code ;
    }

     /* *
     * 获取图像类型
     * 
     * @access  private
     * @param   string  扩展名
     * @return  [mixed] 错误时返回 false
      */
     function  getImageType( $extension ) 
    {
         switch  ( strtolower ( $extension )) 
        {
             case   ' png ' :
                 $information [ ' mime ' ]  =   image_type_to_mime_type (IMAGETYPE_PNG);
                 $information [ ' func ' ]  =   ' imagepng ' ;
                 break ;
             case   ' gif ' :
                 $information [ ' mime ' ]  =   image_type_to_mime_type (IMAGETYPE_GIF);
                 $information [ ' func ' ]  =   ' imagegif ' ;
                 break ;
             case   ' wbmp ' :
                 $information [ ' mime ' ]  =   image_type_to_mime_type (IMAGETYPE_WBMP);
                 $information [ ' func ' ]  =   ' imagewbmp ' ;
                 break ;
             case   ' jpg ' :
             case   ' jpeg ' :
             case   ' jpe ' :
                 $information [ ' mime ' ]  =   image_type_to_mime_type (IMAGETYPE_JPEG);
                 $information [ ' func ' ]  =   ' imagejpeg ' ;
                 break ;
             default :
                 $information   =   false ;
        }
         return   $information ;
    }

     /* *
     * 绘制图像干扰
     * 
     * @access  private
     * @param   resource 图像资源
     * @return  void
      */
     function  paintMolestation( & $im ) 
    {
         //  总象素
         $num_of_pels   =   ceil ( $this -> image[ ' width ' ] * $this -> image[ ' height ' ] / 5 );
         switch  ( $this -> molestation[ ' density ' ]) 
        {
             case   ' fewness ' :
                 $density   =   ceil ( $num_of_pels   /   3 );
                 break ;
             case   ' muchness ' :
                 $density   =   ceil ( $num_of_pels   /   3   *   2 );
                 break ;
             case   ' normal ' :
                 $density   =   ceil ( $num_of_pels   /   2 );
             default :
        }

         switch  ( $this -> molestation[ ' type ' ]) 
        {
             case   ' point ' :
                 $this -> paintPoints( $im ,   $density );
                 break ;
             case   ' line ' :
                 $density   =   ceil ( $density   /   30 );
                 $this -> paintLines( $im ,   $density );
                 break ;
             case   ' both ' :
                 $density   =   ceil ( $density   /   2 );
                 $this -> paintPoints( $im ,   $density );
                 $density   =   ceil ( $density   /   30 );
                 $this -> paintLines( $im ,   $density );
                 break ;
             default :
                 break ;
        }
    }

     /* *
     * 画点
     * 
     * @access  private
     * @param   resource 图像资源
     * @param   int      图像资源
     * @return  void
      */
     function  paintPoints( & $im ,   $quantity ) 
    {
         mt_srand (( double ) microtime () * 1000000 );

         for  ( $i = 0 ;  $i < $quantity ;  $i ++ ) 
        {
             $randcolor   =  imagecolorallocate( $im ,   mt_rand ( 0 , 255 ) ,  
                                             mt_rand ( 0 , 255 ) ,   mt_rand ( 0 , 255 ));
            imagesetpixel( $im ,   mt_rand ( 0 ,   $this -> image[ ' width ' ]) ,  
                           mt_rand ( 0 ,   $this -> image[ ' height ' ]) ,   $randcolor );
        }
    }

     /* *
     * 画线
     * 
     * @access  private
     * @param   resource 图像资源
     * @param   int      图像资源
     * @return  void
      */
     function  paintLines( & $im ,   $quantity ) 
    {
         mt_srand (( double ) microtime () * 1000000 );

         for  ( $i = 0 ;  $i < $quantity ;  $i ++ ) 
        {
             $randcolor   =  imagecolorallocate( $im ,   mt_rand ( 0 , 255 ) ,  
                                             mt_rand ( 0 , 255 ) ,   mt_rand ( 0 , 255 ));
            imageline( $im ,   mt_rand ( 0 ,   $this -> image[ ' width ' ]) ,  
                       mt_rand ( 0 ,   $this -> image[ ' height ' ]) ,  
                       mt_rand ( 0 ,   $this -> image[ ' width ' ]) ,  
                       mt_rand ( 0 ,   $this -> image[ ' height ' ]) ,   $randcolor );
        }
    }

}

?>

 

image.php

<? php
/* *
 * 这个页面用于生成验证码图像
 * 
 * @author  ♂bingo↗ [coolhpy@163.com]
 * @since   2006-6-17
  */

session_start ();
header ( " Cache-Control: no-cache, must-revalidate " );

require ( " ./AuthCode.class.php " );

$auth_code   =   new  AuthCode();

//  定义验证码信息
$arr [ ' code ' ]  =   array (
     ' characters '   =>   ' A-Z,1-9 ' ,  
     ' length '   =>   4 ,
     ' deflect '   =>   true ,
     ' multicolor '   =>   false
);
$auth_code -> setCode( $arr [ ' code ' ]);

//  定义干扰信息
$arr [ ' molestation ' ]  =   array (
     ' type '   =>   ' both ' ,  
     ' density '   =>   ' normal '
);
$auth_code -> setMolestation( $arr [ ' molestation ' ]);

//  定义图像信息
$arr [ ' image ' ]  =   array (
     ' type '   =>   ' gif ' ,  
     ' width '   =>   70 ,  
     ' height '   =>   20
);
$auth_code -> setImage( $arr [ ' image ' ]);

//  定义字体信息
$arr [ ' font ' ]  =   array (
     ' space '   =>   5 ,  
     ' size '   =>   12 ,  
     ' left '   =>   5 ,  
     ' top '   =>   15 ,  
     ' file '   =>   ' ./arial.ttf '
);
$auth_code -> setFont( $arr [ ' font ' ]);

//  定义背景色
$arr [ ' bg ' ]  =   array (
     ' r '   =>   255 ,  
     ' g '   =>   255 ,  
     ' b '   =>   255
);
$auth_code -> setBgColor( $arr [ ' bg ' ]);

//  输出到浏览器
$auth_code -> paint();

//  输出到文件, 文件名中不需要扩展名
//$auth_code->paint('./test');
?>

 

//handle.php

<? php
/* *
 * 这个页面用于对用户输入的验证码进行验证
 * 
 * @author  ♂bingo↗ [coolhpy@163.com]
 * @since   2006-6-21
  */

session_start ();
include ( " ./AuthCode.class.php " );
$auth_code   =   new  AuthCode();

$code_input   =   $_REQUEST [ ' code_input ' ];
$do   =   $_REQUEST [ ' do ' ];

if  ( $do   ==   ' ajax ' ) 
{
     if  ( $auth_code -> validate( $code_input ,   false )) 
    {
         $result   =   ' true ' ;
    }  else  
    {
         $result   =   ' false ' ;
    }
     echo   $result ;
     exit ;
}

if  ( $do   ==   ' form ' ) 
{
     if  ( $auth_code -> validate( $code_input ,   false )) 
    {
         $result   =   ' True ' ;
    }  else  
    {
         $result   =   ' False ' ;
    }
     echo   ' <script language="JavaScript"> ' .
          ' alert(' ' . $result . ' '); ' .
          ' window.open('example.html', '_self', ''); ' .
          ' </script> ' ;
     exit ;
}

?>

 

 

<!--
/**
 * 这是一个实例页
 * 
 * @author  ♂bingo↗ [coolhpy@163.com]
 * @since   2006-6-21
 */
-->
< html >
< head >
< title > Auth_code </ title >
< script  language ="JavaScript" > ...
function createRequest() 
...{
    var request = false;
    try 
    ...{
        request = new XMLHttpRequest();
    } catch (trymicrosoft) 
    ...{
        try 
        ...{
            request = new ActiveXObject("Msxml2.XMLHTTP");
        } catch (othermicrosoft) 
        ...{
            try 
            ...{
                request = new ActiveXObject("Microsoft.XMLHTTP");
            } catch (failed) 
            ...{
                request = false;
            }
        }
    }

    if (!request) 
    ...{
        alert("Error to initial XMLHttpRequest object, so you cannot " + 
              "use AJAX to validate what you inputed!");
    } else 
    ...{
        return request;
    }
}

var req = createRequest();

function fetchData(id) 
...{
    var code_input = document.getElementById(id).value;
    var url = "./handle.php?do=ajax&code_input=" + code_input;
    if (req) 
    ...{
        req.open("GET", url, true);
        req.onreadystatechange = fetchHandle;
        req.send(null);
    }
}

function fetchHandle() 
...{
    if (req.readyState == 4 && req.status == 200) 
    ...{
        var msg = req.responseText;
        obj = document.getElementById('show_msg');
        if (msg == 'true') 
        ...{
            obj.style.color = '#00FF00';
        } else 
        ...{
            obj.style.color = '#FF0000';
        }
        obj.innerHTML = msg;
    }
}
</ script >
< style  type ="text/css" > ...
body, td, lable 
{...}{
    font-family : 'Tahoma, Arial, Helvetica, sans-serif';
    font-size : 12px;
}
</ style >
</ head >

< body >
< form  name ="auth_form"  action ="./handle.php"  method ="post" >
< table  width ="300"  bgcolor ="#999999"  cellpadding ="5"  cellspacing ="1" >
   < tr >
     < td  align ="right"  width ="20%"  bgcolor ="#FFFFFF" > Code:  </ td >
     < td  bgcolor ="#FFFFFF" >< input  type ="text"  id ="code_input"  name ="code_input"  
       size ="10" maxlength ="10"  onkeyup ="javascript:fetchData('code_input');" />
       < img  src ="image.php"  alt ="Click for refresh"  style ="cursor:hand;"  
      onClick ="this.src=this.src"   />   &nbsp;
       < label  id ="show_msg"  style ="color:#FF0000;" ></ label ></ td >
   </ tr >
   < tr >
     < td  align ="center"  colspan ="2"  bgcolor ="#FFFFFF" >< input  type ="hidden"  
      name ="do"  value ="form"   />
       < input  type ="submit"  value ="Submit"   /></ td >
   </ tr >
</ table >
</ form >
</ body >
</ html >