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HomeBackend DevelopmentPHP Tutorialphp生成SessionID和图片校验码的思路和实现代码_php技巧

/****** 产生Session ID ******/
基本的思路: 是把当前微秒的时间获取, 然后产生以个随机数字, 把随机数字和当前时间相加后加密一下, 最后再截取需要的长度
/*
函数名称:create_sess_id()
函数作用:产生以个随机的会话ID
参 数:$len: 需要会话字符串的长度,默认为32位,不要低于16位
返 回 值:返回会话ID
函数作者:heiyeluren
*/
function create_sess_id($len=32)
{
// 校验提交的长度是否合法
if( !is_numeric($len) || ($len>32) || ($len// 获取当前时间的微秒
list($u, $s) = explode(' ', microtime());
$time = (float)$u + (float)$s;
// 产生一个随机数
$rand_num = rand(100000, 999999);
$rand_num = rand($rand_num, $time);
mt_srand($rand_num);
$rand_num = mt_rand();
// 产生SessionID
$sess_id = md5( md5($time). md5($rand_num) );
// 截取指定需要长度的SessionID
$sess_id = substr($sess_id, 0, $len);
return $sess_id;
}


/****** 产生校验码 ******/
思路: 这个思路比较简单,因为考虑独一无二和随机性,我们的校验码就Session ID里面截取一段字符串就可以了,因为我们的SessionID是充分考虑了独一无二的。

/*
函数名称:create_check_code()
函数作用:产生以个随机的校验码
参 数:$len: 需要校验码的长度, 请不要长于16位,缺省为4位
返 回 值:返回指定长度的校验码
函数作者:heiyeluren
*/
function create_check_code($len=4)
{
if ( !is_numeric($len) || ($len>6) || ($len
$check_code = substr(create_sess_id(), 16, $len );
return strtoupper($check_code);
}


/****** 生成校验码的图片 ******/

这个就是一些比较简单的PHP图像编程的东西了,我作的图片和简单。

/*
函数名称:create_check_image()
函数作用:产生一个校验码的图片
参 数:$check_code: 校验码字符串,一般由create_check_code()函数来获得
返 回 值:返回该图片
函数作者:heiyeluren
*/
function create_check_image( $check_code )
{
// 产生一个图片
$im = imagecreate(65,22);
$black = ImageColorAllocate($im, 0,0,0); // 背景颜色
$white = ImageColorAllocate($im, 255,255,255); // 前景颜色
$gray = ImageColorAllocate($im, 200,200,200);
imagefill($im,68,30,$gray);

// 将四位整数验证码绘入图片
imagestring($im, 5, 8, 3, $check_code, $white);
// 加入干扰象素
for($i=0;$i{
$randcolor = ImageColorallocate($im,rand(0,255),rand(0,255),rand(0,255));
imagesetpixel($im, rand()%70 , rand()%30 , $randcolor);
}
// 输出图像
Header("Content-type: image/PNG");
ImagePNG($im);
ImageDestroy($im);
}

这里我们要注意,引用create_check_image()函数的时候,必须在一个单独的文件里,因为输出文件头的时候输出的格式是图像格式,夹杂其他内容,会导致图片无法显示。另外,图片成生函数,你是可以更改的,比如你想改颜色,那么你就把前景色和背景色的生成位置换一下,那么颜色就不一样了,同时也要把校验码的颜色换了,不然背景和校验码都是黑色就显示不出来了。

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