What are some methods for generating random numbers in PHP?-PHP Tutorial-php.cn

This time I will bring you some methods of generating random numbers in PHP, and what are the precautions for generating random numbers in PHP. The following is a practical case, let's take a look.

The first method uses mt_rand()

function GetRandStr($length){ $str='abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'; $len=strlen($str)-1; $randstr=''; for($i=0;$i<$length;$i++){ $num=mt_rand(0,$len); $randstr .= $str[$num]; } return $randstr; } $number=GetRandStr(6); echo $number;

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The second method (fastest)

function make_password( $length = 8 ) { // 密码字符集，可任意添加你需要的字符 $chars = array('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l','m', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y','z', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L','M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y','Z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '!', '@','#', '$', '%', '^', '&', '*', '(', ')', '-', '_', '[', ']', '{', '}', '<', '>', '~', '`', '+', '=', ',', '.', ';', ':', '/', '?', '|'); // 在 $chars 中随机取 $length 个数组元素键名 $keys = array_rand($chars, $length); $password = ''; for($i = 0; $i < $length; $i++) { // 将 $length 个数组元素连接成字符串 $password .= $chars[$keys[$i]]; } return $password; }

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The third way is to get the current timestamp

function get_password( $length = 8 ) { $str = substr(md5(time()), 0, $length);//md5加密，time()当前时间戳 return $str; }

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The fourth way is to scramble the string

function getrandstr(){ $str='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890'; $randStr = str_shuffle($str);//打乱字符串 $rands= substr($randStr,0,6);//substr(string,start,length);返回字符串的一部分 return $rands; }

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//Start creating

Verification code(Generate directly using functions, which is more convenient and fast)

$code = rand(10000, 99999);

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php mt_rand compares the effect of generating 0~1 random decimals

lcg_value description

float lcg_value (void)

lcg_value() returns a pseudo-random number in the range (0, 1). This function combines two congruential generators with periods 2^31 - 85 and 2^31 - 249. The period of this function is equal to the product of these two prime numbers.

Return: pseudo-random number in the range (0, 1).

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Output:

0.11516515851995
0.064684551575297
0.68275174031189
0.55730746529099
0.70215008878091

Two kinds of generation 0~1 random decimal method for comparison

1. Execution time comparison

The running time of executing 100,000 times based on mt_rand() and mt_getrandmax() algorithms

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Output: run time 266.893148 ms

The running time of executing lcg_value() 100,000 times

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Output: run time 86.178064 ms

Execution time Compared with the above, because lcg_value() is directly a native PHP method, and mt_rand() and mt_getrandmax() need to call two methods and need to be calculated, so the execution time of lcg_value() is about 3 times faster.

2. Random effect comparison

Random effect based on mt_rand() and mt_getrandmax() algorithms

=0.5){ imagesetpixel($im, $x, $y, $color1); }else{ imagesetpixel($im, $x, $y, $color2); } } } imagepng($im); imagedestroy($im); ?>

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Random effect of lcg_value()

=0.5){ imagesetpixel($im, $x, $y, $color1); }else{ imagesetpixel($im, $x, $y, $color2); } } } imagepng($im); imagedestroy($im); ?>

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I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!