This time I will bring you some methods of generating random numbers in PHP, and notes on 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;
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; }
The third method is to take the current timetime stamp
function get_password( $length = 8 ) { $str = substr(md5(time()), 0, $length);//md5加密,time()当前时间戳 return $str; }
The fourth way to scramble strings
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; }
//Start creating Verification code (generated directly using a function, which is more convenient and fast)
$code = rand(10000, 99999);
Comparison of the effects of php mt_rand generating 0~1 random decimals
lcg_value description
float lcg_value (void)
lcg_value() returns a pseudo-random number in the range (0, 1). This function combines two congruential generators with periods 2^31 - 85 and 2^31 - 249. The period of this function is equal to the product of these two prime numbers.
Returns: a pseudo-random number in the range (0, 1).
<?php for($i=0; $i<5; $i++){ echo lcg_value().PHP_EOL; } ?>
Output:
0.11516515851995
0.064684551575297
0.68275174031189
0.55730746529099
0.70215008878091
Comparison of two methods of generating random decimals from 0 to 1
1.Execution time comparison
The running time of executing the algorithm based on mt_rand() and mt_getrandmax() 100,000 times
<?php /** * 生成0~1随机小数 * @param Int $min * @param Int $max * @return Float */ function randFloat($min=0, $max=1){ return $min + mt_rand()/mt_getrandmax() * ($max-$min); } // 获取microtime function get_microtime(){ list($usec, $sec) = explode(' ', microtime()); return (float)$usec + (float)$sec; } // 记录开始时间 $starttime = get_microtime(); // 执行10万次获取随机小数 for($i=0; $i<100000; $i++){ randFloat(); } // 记录结束时间 $endtime = get_microtime(); // 输出运行时间 printf("run time %f ms\r\n", ($endtime-$starttime)*1000); ?>
Output: run time 266.893148 ms
Running time of executing lcg_value() 100,000 times
<?php // 获取microtime function get_microtime(){ list($usec, $sec) = explode(' ', microtime()); return (float)$usec + (float)$sec; } // 记录开始时间 $starttime = get_microtime(); // 执行10万次获取随机小数 for($i=0; $i<100000; $i++){ lcg_value(); } // 记录结束时间 $endtime = get_microtime(); // 输出运行时间 printf("run time %f ms\r\n", ($endtime-$starttime)*1000); ?>
Output: run time 86.178064 ms
Comparison of execution time, because lcg_value() is directly a native PHP method, while 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. Comparison of random effects
Random effect based on mt_rand() and mt_getrandmax() algorithms
<?php /** * 生成0~1随机小数 * @param Int $min * @param Int $max * @return Float */ function randFloat($min=0, $max=1){ return $min + mt_rand()/mt_getrandmax() * ($max-$min); } header('content-type: image/png'); $im = imagecreatetruecolor(512, 512); $color1 = imagecolorallocate($im, 255, 255, 255); $color2 = imagecolorallocate($im, 0, 0, 0); for($y=0; $y<512; $y++){ for($x=0; $x<512; $x++){ $rand = randFloat(); if(round($rand,2)>=0.5){ imagesetpixel($im, $x, $y, $color1); }else{ imagesetpixel($im, $x, $y, $color2); } } } imagepng($im); imagedestroy($im); ?>
The random effect of lcg_value()
<?php header('content-type: image/png'); $im = imagecreatetruecolor(512, 512); $color1 = imagecolorallocate($im, 255, 255, 255); $color2 = imagecolorallocate($im, 0, 0, 0); for($y=0; $y<512; $y++){ for($x=0; $x<512; $x++){ $rand = lcg_value(); if(round($rand,2)>=0.5){ imagesetpixel($im, $x, $y, $color1); }else{ imagesetpixel($im, $x, $y, $color2); } } } imagepng($im); imagedestroy($im); ?>
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!
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