Summary of Methods of Generating Random Numbers in PHP

  • 2021-09-12 00:35:23
  • OfStack

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; 

Method 2 (Fastest)


function make_password( $length = 8 ) 
{ 
 //  Password character set, you can add any characters you need  
 $chars = array('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 
 'i', 'j', 'k', 'l','m', 'n', 'o', 'p', 'q', 'r', 's', 
 't', 'u', 'v', 'w', 'x', 'y','z', 'A', 'B', 'C', 'D', 
 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L','M', 'N', 'O', 
 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y','Z', 
 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '!', 
 '@','#', '$', '%', '^', '&', '*', '(', ')', '-', '_', 
 '[', ']', '{', '}', '<', '>', '~', '`', '+', '=', ',', 
 '.', ';', ':', '/', '?', '|'); 
 //  In  $chars  Random selection in  $length  Array element key names  
 $keys = array_rand($chars, $length); 
 $password = ''; 
 for($i = 0; $i < $length; $i++) 
 { 
  //  Will  $length  Array elements are concatenated into strings  
  $password .= $chars[$keys[$i]]; 
 } 
 return $password; 
} 

The third is to take the time stamp at that time


function get_password( $length = 8 ) 
{ 
 $str = substr(md5(time()), 0, $length);//md5 Encryption, time() Current timestamp  
 return $str; 
} 

The fourth scrambling string


function getrandstr(){ 
$str='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890'; 
$randStr = str_shuffle($str);// Scramble a string  
$rands= substr($randStr,0,6);//substr(string,start,length); Returns the of the string 1 Part  
return $rands; 
} 

//Start creating verification code (directly generated by function, which is more convenient and quick)


$code = rand(10000, 99999); 

Comparison of the effects of php mt_rand on generating 0 ~ 1 random decimals

lcg_value Description

float lcg_value ( void )

lcg_value () returns a pseudo-random number with a range of (0, 1). This function combines two congruence 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: Pseudorandom numbers 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 for generating 0 ~ 1 random decimals

1. Execution time comparison

Runtime to execute 100,000 times based on mt_rand () and mt_getrandmax () algorithms


<?php
/**
 *  Generate 0~1 Random decimal 
 * @param Int $min
 * @param Int $max
 * @return Float
 */
function randFloat($min=0, $max=1){
 return $min + mt_rand()/mt_getrandmax() * ($max-$min);
}

//  Get microtime
function get_microtime(){
 list($usec, $sec) = explode(' ', microtime());
 return (float)$usec + (float)$sec;
}

//  Record start time 
$starttime = get_microtime();

//  Execute 10 Get random decimals ten thousand times 
for($i=0; $i<100000; $i++){
 randFloat();
}

//  Record end time 
$endtime = get_microtime();

//  Output runtime 
printf("run time %f ms\r\n", ($endtime-$starttime)*1000);
?>

Output: run time 266.893148 ms

Run time of executing lcg_value () 100,000 times


<?php
//  Get microtime
function get_microtime(){
 list($usec, $sec) = explode(' ', microtime());
 return (float)$usec + (float)$sec;
}


//  Record start time 
$starttime = get_microtime();


//  Execute 10 Get random decimals ten thousand times 
for($i=0; $i<100000; $i++){
 lcg_value();
}


//  Record end time 
$endtime = get_microtime();


//  Output runtime 
printf("run time %f ms\r\n", ($endtime-$starttime)*1000);
?>

Output: run time 86.178064 ms

Because lcg_value () is directly the native method of php, and mt_rand () and mt_getrandmax () need to call two methods and need to be evaluated, the execution time of lcg_value () is about three times faster.

2. Random effect comparison

Random Effects Based on mt_rand () and mt_getrandmax () Algorithms


<?php
/**
 *  Generate 0~1 Random decimal 
 * @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);
?>

Random effects 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);
?>


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