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php随机数字代码 php产生随机数字的方法

Jun 13, 2016 am 11:37 AM
php code Can consult Base number method have friend of question random

今天,有朋友咨询烈火PHP随机数字的问题,这是PHP的基础问题,大家可以参考一下烈火提供的PHP手册,由于时间关系,小编也懒的写,在网上找了一些例子,综合在一起,希望对大家有所帮助吧,如有问题请在下面说出来。

//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
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
但是如果用一个随机数做种子,那每次运行结果就近似于随机的

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,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,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,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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