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深入PHP获取随机数字和字母的方法详解

Jun 06, 2016 pm 08:30 PM
php letter random numbers

本篇文章是对PHP获取随机数字和字母的方法进行了详细的分析介绍,需要的朋友参考下

第一种方法

复制代码 代码如下:


  $FileID=date("Ymd-His") . '-' . rand(100,999);
  //$FileID为 20100903-132121-908 这样的的随机数
?>


第二种方法

复制代码 代码如下:


function randomkeys($length) {
$returnStr='';
$pattern = '1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLOMNOPQRSTUVWXYZ';
for($i = 0; $i $returnStr .= $pattern {mt_rand ( 0, 61 )}; //生成php随机数
}
return $returnStr;
}
echo randomkeys(4);
?>


第三种方法

复制代码 代码如下:


//seed用户自定义函数以微秒作为种子
function seed()
{
list($msec, $sec) = explode(' ', microtime());
return (float) $sec;
}
//播下随机数发生器种子,用srand函数调用seed函数的返回结果
srand(seed());
//输出产生的随机数,随机数的范围为10-100
echo rand(10,100);
?>


上面这个和下面这个不是没什么不同吗?都是随机输出10-100之间的数,新人学习,可能问的太简单了呵呵

复制代码 代码如下:


echo rand(10,100);
?>
mt_rand(10,100);


srand是种子,如果不设的话默认是1
rand一般是利用种子做参数的一种固定的运算
你试一下就知道了,不设种子或者设一个固定的种子,运行rand
然后再关了浏览器再开,再运行rand
你会发现结果一直是一样的
先说rand()函数吧,rand([int min], [int max])
本函数从min和max之间取一个随机数。若没有指定随机数的最大及最小范围,服务器空间,本函数会自动的从0到RAND_MAX中取一个随机数。
但是如果只用rand()这个函数,香港虚拟主机,随机数的乱度很大,每次在取随机数之前最好使用srand()函数,以配置新的随机数种子。
解释一下下面这个用法(一般都是这样用这两个函数的):
srand((double)microtime()*1000000);
$rand_number= rand();
microtime()返回了两个值:当前毫秒和时间戳,我们要提取随机数,只能从毫秒中取一个随机数,(double)microtime()就只返回当前的毫秒值。
microtime()是以秒为单位的毫秒数,因而值都是小数,乘以1000000将其换算为整数

它们的工作流程如下:
(1):首先,给srand()提供一个”种子”;,它是一个unsigned_int类型的值。
(2):_然后,香港空间,调用rand(),它会根据提供给srand()的值返回一个随机数(范围在_0~32767之间)
(3):根据需要多次调用rand(),不断得到新的随机数。
(4):无论什么时候可以给srand()提供一个新的“种子”,从而进一步“随机化”rand()的
输出结果。

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