mt_rand

(PHP 4, PHP 5)

mt_randГенерирует случайное значение методом mt

Описание

int mt_rand ( void )
int mt_rand ( int $min , int $max )

Многие генераторы случайных чисел в старых библиотеках имеют сомнительные или неизвестные характеристики, а также работают довольно медленно. По умолчанию, PHP использует генератор случайных чисел libc с помощью функции rand(). Функция mt_rand() представляет собой удобную замену этой функции. Она использует генератор случайных чисел с известными характеристиками, основанный на "» Вихре Мерсенна", который генерирует случайные числа в среднем в четыре раза быстрее, чем libc rand().

Вызванная без необязательных параметров min и max, функция mt_rand() возвращает псевдослучайное значение между 0 и mt_getrandmax(). Если вам нужно, например, случайное число между 5 и 15 (включительно), используйте вызов mt_rand(5,15)

Список параметров

min

Необязательный параметр: минимальное значение случайного числа (по умолчанию: 0)

max

Необязательный параметр: максимальное значение случайного числа (по умолчанию: mt_getrandmax())

Возвращаемые значения

Случайное целое значение между min (или 0) и max (или mt_getrandmax(), включительно)

Список изменений

Версия Описание
4.2.0Генератор случайных чисел инициализируется автоматически.

Примеры

Пример #1 Пример использования mt_rand()

<?php
echo mt_rand() . "\n";
echo 
mt_rand() . "\n";

echo 
mt_rand(515);
?>

Результатом выполнения данного примера будет что-то подобное:

1604716014
1478613278
6

Примечания

Предостережение

Распределение значений, возвращаемых mt_rand(), отдает предпочтение четным числам на 64-битных сборках PHP, если параметр max больше 2^32.

Смотрите также

  • mt_srand() - Переинициализирует генератор случайных чисел mt
  • mt_getrandmax() - Показывает максимально возможное значение случайного числа
  • rand() - Генерирует случайное число

Коментарии

<?php
//
// Generates a random string with the specified length
// Chars are chosen from the provided [optional] list
//
function simpleRandString($length=16$list="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"){
   
mt_srand((double)microtime()*1000000);
   
$newstring="";

    if(
$length>0){
        while(
strlen($newstring)<$length){
           
$newstring.=$list[mt_rand(0strlen($list)-1)];
        }
    }
    return 
$newstring;
}

//
// Generates a random string with the specified length
// Includes: a-z, A-Z y 0-9
//
function randString($length=16) {
   
$newstring="";
   if(
$length>0) {
       while(
strlen($newstring)<$length) {
           
$randnum mt_rand(0,61);
           if (
$randnum 10) {
               
$newstring.=chr($randnum+48);
           } elseif (
$randnum 36) {
               
$newstring.=chr($randnum+55);
           } else {
               
$newstring.=chr($randnum+61);
           }
       }
   }
   return 
$newstring;
}
?>
2002-03-02 14:38:23
http://php5.kiev.ua/manual/ru/function.mt-rand.html
The following function will create a random base64 encoded key, this is very useful for password reset schemes or anything where you want a random string.  To compare the string either compare the base64 encoded value or base64_decode it and compare that.

I do not use md5 because md5 results in only 1-9 and a-f in the string or 32^16 possibilities, by using the extended ASCII table and shuffling the array I am able to get a minimum of 32^127 possibilities with a 32 character string, using a longer string will make your value harder to guess still. A lot of machiens will have 32^255 possibilities in a decoded string.

<?php
function MakeResetKey($min_length 32$max_length 64)
{
   
$key '';

   
// build range and shuffle range using ASCII table
   
for ($i=0$i<=255$i++) {
     
$range[] = chr($i);
   }

   
// shuffle our range 3 times
   
for ($i=0$i<=3$i++) {
     
shuffle($range);
   }

     
// loop for random number generation
   
for ($i 0$i mt_rand($min_length$max_length); $i++) {
     
$key .= $range[mt_rand(0count($range))];
   }

   
$return base64_encode($key);

   if (!empty(
$return)) {
      return 
$return;
   } else {
      return 
0;
   }
}
?>
2003-06-04 16:49:19
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Автор:
Here is a example of a very small, compact, quite random-random string generator. It will make a string with uppercase & lowercase letters, with numbers. You simply need to set $len in the for() structure, and then the string will be in $r.  It has been designed for size, while it's still quite fast.  Mind the wrapping, it should be 1 line.

<?php 
for($len=8,$r='';strlen($r)<$len;$r.=chr(!mt_rand(0,2)?
mt_rand(48,57):(!mt_rand(0,1)?mt_rand(65,90):mt_rand
(97,122))));
?>

Armond Carroll
2004-02-11 07:27:45
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Running the output of Mersenne Twister through an unkeyed secure hash is NOT a good way to make it secure, because it'll still have a relatively small internal state which, if recovered, would allow reproduction of the keystream.  A better idea would be to encrypt the output with a keyed encryption algorithm - but if you were going to do that, you wouldn't need a psuedorandom number generator at all, because a counter would be just as good.
2005-01-23 17:47:14
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Allows characters 0-9, a-z
Weighted (and tested) ok.

<?php
function generate_string ($length 20)
{
   
$nps "";
    for(
$i=0;$i<$length;$i++)
    {
       
$nps .= chr( (mt_rand(136) <= 26) ? mt_rand(97122) : mt_rand(4857 ));
    }
    return 
$nps;
}
?>
2005-04-16 05:46:32
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Re: solenoid at hotmail dot united dot kingdom

In theory method shown by selenoid can lead to infinite loop. The correct method would be:

<?php
$randomNumbers 
= array();
for (
$i 0i<30; ++$i$randomNumbers[] = $i;
shuffle($randomNumbers);
for (
$i 20$i<30; ++$i) unset($randomNumbers[$i]);
$randomNumbers array_values($randomNumbers);
?>

The last two lines may be in some cases removed.
2005-05-24 20:00:28
http://php5.kiev.ua/manual/ru/function.mt-rand.html
You really shouldn't generate a number to determine the _type_ of the char, then the char itself.  If security is an issue for you, and you want to maintain as much entropy as possible, you should use a function similar to the one below.  Since this seems to be getting repeated over-and-over, I explained (beat into the ground?) the issue on http://www.codeaholics.com/randomCode.php

The code:
<?php
////
// Returns a random code of the specified length, containing characters that are
// equally likely to be any of the digits, uppercase letters, or  lowercase letters.
//
// The default length of 10 provides 839299365868340224 (62^10) possible codes.
//
// NOTE: Do not call wt_srand().  It is handled automatically in PHP 4.2.0 and above
//       and any additional calls are likely to DECREASE the randomness.
////
function randomCode($length=10){
   
$retVal "";
    while(
strlen($retVal) < $length){
       
$nextChar mt_rand(061); // 10 digits + 26 uppercase + 26 lowercase = 62 chars
       
if(($nextChar >=10) && ($nextChar 36)){ // uppercase letters
           
$nextChar -= 10// bases the number at 0 instead of 10
           
$nextChar chr($nextChar 65); // ord('A') == 65
       
} else if($nextChar >= 36){ // lowercase letters
           
$nextChar -= 36// bases the number at 0 instead of 36
           
$nextChar chr($nextChar 97); // ord('a') == 97
       
} else { // 0-9
           
$nextChar chr($nextChar 48); // ord('0') == 48
       
}
       
$retVal .= $nextChar;
    }
    return 
$retVal;
}
?>
2005-07-22 09:31:14
http://php5.kiev.ua/manual/ru/function.mt-rand.html
i did the following, to generate a few random-numbers out of a total amount of numbers, but to create different random-numbers and not double or tripple.
for example i use it to generate 10 random-pics out of 150, and do shurely generate not twice the same...

<?php
$total 
6// available numbers (of pictures)
$randanzahl 6//number of random-number to generate out of $total

function checkifdouble($ran,$i) {
        for(
$j=1$j<$i$j++) {
                if(
$ran[$j]==$ran[$i]) {
                       
$ergebnis="true";
                        break;
                } 
//endif
               
else {
                       
$ergebnis="false";
                } 
//endelse
       
//endfor
return $ergebnis;
}

for (
$i=1$i<=$randanzahl$i++) {
       
$ran[$i] = mt_rand(1$total);
       if (
$i>1) {
               while(
checkifdouble($ran,$i)=="true") {
                       
$ran[$i] = mt_rand(1$total);
                       
$v=checkifdouble($ran,$i);
                       echo(
$v);
               } 
//endif
       
}
       echo(
$ran[$i]."<br>");

//enfor
?>

this version is easily for debugging and adaption!
maybe there is a very shorter version...
2005-10-08 12:12:13
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Since many people wrote little scripts to generate random sequences, I'll also give mine (which is slightly faster since it makes use of strlen only once, and uses strings instead of arrays) :

<?php
function code($nc$a='abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789') {
   
$l=strlen($a)-1$r='';
    while(
$nc-->0$r.=$a{mt_rand(0,$l)};
    return 
$r;
}
?>
2006-08-25 08:44:34
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Автор:
Shouldn't it be a greater than (>) sign rather than a not equal (!=) sign? Because you're just checking to see if it is exactly six. So if it is 7 it, won't try to fix it. So wouldn't this be better?
<?
//....
if (strlen($random_hex) < "6"// sometimes it returns an only 5, or less, char Hex-Code,
   
hexcode();        // so the function has to be repeat
elseif (strlen($random_hex) > "6"// sometimes it returns 7 or more characters
//...I don't know how to make it do only six, but your code seems to only check to make sure it doesn't do less than 6; nothing to counter doing more than 6.... so here would be some code to reduce the size back to 6 if it went over.
else
   echo 
$random_hex// returns the Hex-Code
}
//...
?>
2006-11-06 02:40:37
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Автор:
>Running the output of Mersenne Twister through an unkeyed >secure hash is NOT a good way to make it secure, because it'll >still have a relatively small internal state which, if recovered, >would allow reproduction of the keystream.  A better idea >would be to encrypt the output with a keyed encryption >algorithm - but if you were going to do that, you wouldn't >need a psuedorandom number generator at all, because a >counter would be just as good.

Not true. Mersenne Twister has an ENORMOUS amount of internal state - 4992 bits, bigger than practically any cipher's key length. The point of a secure random number generator is that you cannot predict future outputs based on past OUTPUTS, which is why a hash is applied. Clearly you can predict the future output of any pseudorandom number generator if you can acquire the internal state - a better algorithm will never solve this problem. If you use keyed encryption, recovering the key allows you to predict future outputs.
2006-11-10 13:35:33
http://php5.kiev.ua/manual/ru/function.mt-rand.html
In answer to David and pHp_n00b, about generating a random 6 characters hexadecimal string...

Well, the easiest solution would be :
<?php
$rand 
mt_rand(0x0000000xffffff); // generate a random number between 0 and 0xffffff
$rand dechex($rand 0xffffff); // make sure we're not over 0xffffff, which shouldn't happen anyway
$rand str_pad($rand6'0'STR_PAD_LEFT); // add zeroes in front of the generated string
echo $rand;
?>

Some examples of generated stuff :
8514d2
3188ae
028f3e
444397
1de508
071662

You can easily make a function from this code.
2006-11-20 09:34:26
http://php5.kiev.ua/manual/ru/function.mt-rand.html
a better (and likely faster) way to generate a random 6-digit hex string:

<?php
$num 
mt_rand 00xffffff ); // trust the library, love the library...
$output sprintf "%06x" $num ); // muchas smoochas to you, PHP!
return $output;
?>

The mt_rand function won't give you a number outside the bounds you asked for -- no need to and-off the top bits -- and the sprintf function has params for length-padding & hexidecimal output.  It's likely faster because most of the work is being done by the wicked fast C functions that PHP sits on top of, though YMMV in that dept.
2007-02-08 00:44:38
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Here is my Function to generate an Array with unique random Numbers between "$from" and "$to".

function random_number_array($count, $from, $to){
   for($i=$from;$i<$to;$i++){
    $number_array[] = $i;
   }
   $random_number_array = array();
   mt_srand ((double) microtime() * 1000000);
   for($i=0;$i<$count;$i++){
      $random_number            = mt_rand(0,count($number_array)-1);
      $key_to_insert_and_delete = array_search($random_number, $number_array);
      $random_number_array[$i]    = $number_array[$key_to_insert_and_delete];
      array_splice($number_array, $key_to_insert_and_delete, 1);
   }
   // Array $random_number_array with $count random Numbers, between $from and $to
   return $random_number_array;
}

I hope its helping you.

Greetings

Rene Andris
2007-03-10 13:50:05
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Here is my Function to generate an Array with unique random Numbers between "$from" and "$to".

<?php
function random_number_array($count$from$to){
   for(
$i=$from;$i<$to;$i++){
   
$number_array[] = $i;
   }
   
$random_number_array = array();
   
mt_srand ((double) microtime() * 1000000);
   for(
$i=0;$i<$count;$i++){
     
$random_number            mt_rand(0,count($number_array)-1);
     
$key_to_insert_and_delete array_search($random_number$number_array);
     
$random_number_array[$i]    = $number_array[$key_to_insert_and_delete];
     
array_splice($number_array$key_to_insert_and_delete1);
   }
   
// Array $random_number_array with $count random Numbers, between $from and $to
   
return $random_number_array;
}
?>

I hope its helping you.

Greetings

Rene Andris
2007-03-10 16:00:14
http://php5.kiev.ua/manual/ru/function.mt-rand.html
The algorithm used by mt_rand() changed in PHP 5.2.1. If you are relying on getting the same sequence from mt_rand() after calling mt_srand() with a known seed, upgrading to PHP 5.2.1 will break your code. See http://bugs.php.net/bug.php?id=40724 for something of an explanation; there is no workaround.
2007-03-21 11:18:58
http://php5.kiev.ua/manual/ru/function.mt-rand.html
mt_rand function returns just a whole numbers. If you want a random float, then here's an elegant way:

<?php
function random_float ($min,$max) {
   return (
$min+lcg_value()*(abs($max-$min)));
}
?>
2007-06-16 03:42:49
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Автор:
performance: for a repetitive task, it's much faster not to use the limit parameters, as shown below. just use the % operator.

$t=microtime(true);
for($i=0;$i<1000000;$i++)
 mt_rand()%3;
echo microtime(true)-$t;

echo '|';

$t=microtime(true);
for($i=0;$i<1000000;$i++)
 mt_rand(0,2);
echo microtime(true)-$t;

echo '|';

$t=microtime(true);
for($i=0;$i<1000000;$i++)
 mt_rand();
echo microtime(true)-$t;

output: 0.316797971725|0.442242145538|0.253082036972
2007-11-13 08:42:35
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Автор:
Do not rely on the strength of any 'home-brewed' cryptographic algorithm, such as the one posted by dmoree at coker dot edu.  Algorithms such as MD5 and SHA-1 have been the subject of intense academic research and have known security properties.

While it is true that MD5 and SHA-1 are generally no longer recommended for use in new cryptosystems, there are newer algorithms such as SHA-256 that address the older algorithms' weaknesses.  These newer algorithms have not received quite as much scrutiny as their older counterparts, but have still been studied much more carefully than your home-brewed algorithm, most likely.

Dmoree at coker dot edu's concern about rainbow tables is best addressed by a properly applied salting technique.  Every bit of 'salt' added to a cryptographic hash effectively extends the complexity of the password and thus the size of the rainbow table needed to crack it.

Furthermore, wisely chosen password strength policies can mitigate such attacks.
2008-02-13 11:24:15
http://php5.kiev.ua/manual/ru/function.mt-rand.html
mt_rand() is not faster than rand() !

Tested over 100'000 iterations, with none/various/random arguments, mt_rand is always 3% slower than rand().
2008-03-29 06:01:22
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Автор:
Below, andrei suggested a function for generating a list of unique integers, randomly arranged.  In response to a note below that his solution is inefficient, I'm providing an O(N) solution which should be much more efficient, yet still yield a good guarantee of producing randomly ordered integers.

<?php
function SwapShuffle($min$max) {
 
$last $max $min;

  for (
$i=0$i<=$last$i++) {
   
$arr[$i] = $min $i;
  }

  for (
$run=0$run<7$run++) {
    for (
$i=0$i<=$last$i++) {
     
$target mt_rand(0$last);
     
$swap $arr[$target];
     
$arr[$target] = $arr[$i];
     
$arr[$i] = $swap;
    }
  }

  return 
$arr;
}

// Call as:
$result SwapShuffle(1030);
foreach (
$result as $num) {
  echo 
"$num\n";
}
?>
2008-04-17 04:14:00
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Автор:
If you need some pseudorandom bits for security or cryptographic purposes (e.g.g., random IV for block cipher, random salt for password hash) mt_rand() is a poor source.  On most Unix/Linux and/or MS-Windows platforms you can get a better grade of pseudorandom bits from the OS or system library, like this:

<?php
// get 128 pseudorandom bits in a string of 16 bytes

$pr_bits '';

// Unix/Linux platform?
$fp = @fopen('/dev/urandom','rb');
if (
$fp !== FALSE) {
   
$pr_bits .= @fread($fp,16);
    @
fclose($fp);
}

// MS-Windows platform?
if (@class_exists('COM')) {
   
// http://msdn.microsoft.com/en-us/library/aa388176(VS.85).aspx
   
try {
       
$CAPI_Util = new COM('CAPICOM.Utilities.1');
       
$pr_bits .= $CAPI_Util->GetRandom(16,0);

       
// if we ask for binary data PHP munges it, so we
        // request base64 return value.  We squeeze out the
        // redundancy and useless ==CRLF by hashing...
       
if ($pr_bits) { $pr_bits md5($pr_bits,TRUE); }
    } catch (
Exception $ex) {
       
// echo 'Exception: ' . $ex->getMessage();
   
}
}

if (
strlen($pr_bits) < 16) {
   
// do something to warn system owner that
    // pseudorandom generator is missing
}
?>

NB: it is generally safe to leave both the attempt to read /dev/urandom and the attempt to access CAPICOM in your code, though each will fail silently on the other's platform.  Leave them both there so your code will be more portable.
2008-06-06 02:31:15
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Re: keith at ourwebsite dot ca

Here's another way to do it, in one line :)
<?php
echo '#' str_padbase_convertmt_rand(0, ( 255*255*255) ), 1016 ), 6'0' ) . "\n";
?>

str_pad is there in case mt_rand chooses a number that will generate a hex value with less than 6 characters. (you could leave that out but it's not a very clean way to write the hex colors is it :)
2008-08-18 18:11:40
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Автор:
Re: euxneks at NOSPAMgmail dot com

You might also want to add STR_PAD_LEFT and have:

<?php
echo '#' str_padbase_convertmt_rand(0, ( 255*255*255) ), 1016 ), 6'0'STR_PAD_LEFT) . "\n";
?>
2008-08-27 20:14:11
http://php5.kiev.ua/manual/ru/function.mt-rand.html
just another example: both of these routines return a random decimal number between -1 and 1... since rand() only returns a max 'integer' value while mt_rand() return a max 'long' value -- at least on some platforms -- mt_rand() could be the better precision choice for some on any variation to this routine (but i don't think it matters here):

<?php
echo "-1 to 1 rand() value: ". (rand(getrandmax()*-1,getrandmax())/getrandmax()). "\n<br/>";
echo 
"-1 to 1 mt_rand() value: ". (mt_rand(mt_getrandmax()*-1,mt_getrandmax())/mt_getrandmax()). "\n";
?>
2009-02-19 11:13:51
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Автор:
Just another random password generator. Assembles passwords such as these:

N_v85kA2_s
8k4jz94_H0
30824n6VcN

useful for... whatever. ;)

$underscores holds the maximum allowed number of underscores. Default is two. The function is programmed to not add an underscore at the beginning or end of the password, right after another underscore, or if the maximum # has already been used.

$length holds the length you want the password to be. Default is 10 characters long.

<?php
function alphanumericPass()
{   
   
// Do not modify anything below here
   
$underscores 2// Maximum number of underscores allowed in password
   
$length 10// Length of password
   
   
$p ="";
    for (
$i=0;$i<$length;$i++)
    {   
       
$c mt_rand(1,7);
        switch (
$c)
        {
            case (
$c<=2):
               
// Add a number
               
$p .= mt_rand(0,9);   
            break;
            case (
$c<=4):
               
// Add an uppercase letter
               
$p .= chr(mt_rand(65,90));   
            break;
            case (
$c<=6):
               
// Add a lowercase letter
               
$p .= chr(mt_rand(97,122));   
            break;
            case 
7:
                 
$len strlen($p);
                if (
$underscores>0&&$len>0&&$len<($length-1)&&$p[$len-1]!="_")
                {
                   
$p .= "_";
                   
$underscores--;   
                }
                else
                {
                   
$i--;
                    continue;
                }
            break;       
        }
    }
    return 
$p;
}
?>
2009-08-04 18:45:31
http://php5.kiev.ua/manual/ru/function.mt-rand.html
The following function generates a string of arbitrary length (with limitations), composed of random PHP characters (i.e. each an 8-bit value - a byte). Suitable for generating random session strings. Encode as Base64 to transmit over network, where required.

** The function is pretty much one of the fastest (if not THE fastest) methods of generating random strings, as opposed to numerous examples given on this page which go about with char-by-char generation. Sloppy benchmarks estimate a factor of 10 speedup. Keep your websites lean, people. **

The only thing to keep in mind is that, by design, it outputs 8-bit characters, and thus the generated string is not automatically suitable for transmission with various network protocols, unless altered, f.e. URL- or Base64- encoded. Also, again by design, the length of the string is a multiple of 4 characters/bytes. The version below produces a 24 character long string. This will also give you a clean input to get a 32 character long Base64 encoded variant of it.

<?php

function gen_rand_str_24()
{
     return 
pack('N6'mt_rand(), mt_rand(), mt_rand(),
         
mt_rand(), mt_rand(), mt_rand());
}

?>

I leave it an exercise to the reader to write a generic (i.e. arbitrary double word length, not 6 dwords as in above) version of it.
2010-01-15 09:59:31
http://php5.kiev.ua/manual/ru/function.mt-rand.html
A class to generate 99.5% unqiue strings. I found that there is only one or two characters common between two subsequent strings.

<?php

class Local_RandomString {
 
  protected 
$_length;
  protected 
$_prevRand;

  public function 
__construct($length 15) {
   
   
$this->_length $length;

  }

  public function 
getRand() {
   
   
$randStr null;   
   
$args[] = 'N' $this->_length;

    for(
$i 0$i $this->_length$i++) {
     
$args[] = mt_rand();     
    }
   
   
$randStr substr(base64_encode((call_user_func_array('pack'$args))), 1$this->_length);
   
$this->_prevRand $randStr;
    return 
$randStr;

  }

  public function 
setLength($l) {
   
   
$this->_length = (int) $l;
   
    if(
$this->_length <= 0) {
      throw new 
Exception('Invalid random string length');
    }

  }

  public function 
getPrevRand() {
   
    return 
$this->_prevRand;

  }

}
?>
2010-05-19 03:20:45
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Автор:
If you need a predictable set of numbers for a given seed, you may use the following Pure-PHP implementation of a Mersenne Twister

<?php
class Mersenne_Twister
{
  private 
$state = array ();
  private 
$index 0;

  public function 
__construct($seed null) {
    if (
$seed === null)
     
$seed mt_rand();

   
$this->setSeed($seed);
  }

  public function 
setSeed($seed) {
   
$this->state[0] = $seed 0xffffffff;

    for (
$i 1$i 624$i++) {
     
$this->state[$i] = (((0x6c078965 * ($this->state[$i 1] ^ ($this->state[$i 1] >> 30))) + $i)) & 0xffffffff;
    }

   
$this->index 0;
  }

  private function 
generateTwister() {
    for (
$i 0$i 624$i++) {
     
$y = (($this->state[$i] & 0x1) + ($this->state[$i] & 0x7fffffff)) & 0xffffffff;
     
$this->state[$i] = ($this->state[($i 397) % 624] ^ ($y >> 1)) & 0xffffffff;

      if ((
$y 2) == 1) {
       
$this->state[$i] = ($this->state[$i] ^ 0x9908b0df) & 0xffffffff;
      }
    }
  }

  public function 
getNext($min null$max null) {
    if ((
$min === null && $max !== null) || ($min !== null && $max === null))
      throw new 
Exception('Invalid arguments');

    if (
$this->index === 0) {
     
$this->generateTwister();
    }

   
$y $this->state[$this->index];
   
$y = ($y ^ ($y >> 11)) & 0xffffffff;
   
$y = ($y ^ (($y << 7) & 0x9d2c5680)) & 0xffffffff;
   
$y = ($y ^ (($y << 15) & 0xefc60000)) & 0xffffffff;
   
$y = ($y ^ ($y >> 18)) & 0xffffffff;

   
$this->index = ($this->index 1) % 624;

    if (
$min === null && $max === null)
      return 
$y;

   
$range abs($max $min);

    return 
min($min$max) + ($y % ($range 1));
  }
}
?>
2010-08-10 12:16:39
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Автор:
Fast, pseudo-random binary data generation using mt_rand():

<?php

function rnd_bin$length )
{
    while( @
$c++ * 16 $length )
        @
$tmp .= md5mt_rand(), true );
    return 
substr$tmp0$length );
}

?>
2010-12-25 08:14:01
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Another good way to get a random float is to divide the result of mt_rand.
Let's say we want a float between 0.75 and 1.25.

<?php

$i 
mt_rand(75,125) / 100;

?>
2011-09-02 14:12:52
http://php5.kiev.ua/manual/ru/function.mt-rand.html
To quickly build a human-readable random string for a captcha per example :

<?php

function random($length 8)
{     
   
$chars 'bcdfghjklmnprstvwxzaeiou';
   
    for (
$p 0$p $length$p++)
    {
       
$result .= ($p%2) ? $chars[mt_rand(1923)] : $chars[mt_rand(018)];
    }
   
    return 
$result;
}

?>

Note that I have removed q and y from $chars to avoid readability problems.
2011-11-24 06:43:22
http://php5.kiev.ua/manual/ru/function.mt-rand.html
i wanted to spot out the big difference between rand and mt_rand when producing images using randomness as noise.

for example this is a comparation between rand and mt_rand on a 400x400 pixel png: http://oi43.tinypic.com/vwtppl.jpg

code:
<?php
header
("Content-type: image/png");
$sizex=800;
$sizey=400;

$img imagecreatetruecolor($sizex,$sizey);
$ink imagecolorallocate($img,255,255,255);

for(
$i=0;$i<$sizex/2;$i++) {
  for(
$j=0;$j<$sizey;$j++) {
 
imagesetpixel($imgrand(1,$sizex/2), rand(1,$sizey), $ink);
  }
}
 
for(
$i=$sizex/2;$i<$sizex;$i++) {
  for(
$j=0;$j<$sizey;$j++) {
 
imagesetpixel($imgmt_rand($sizex/2,$sizex), mt_rand(1,$sizey), $ink);
  }
}

imagepng($img);
imagedestroy($img);
?>

the differences reduce when reducing the pixels of the image.. infact for a 100x100 pixel image the noise produced from the rand function is much more realistic than how it is for a 400x400 image: http://oi39.tinypic.com/5k0row.jpg

(rand is on the left, mt_rand on the right)
2012-03-01 10:44:27
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Автор:
Another graphical comparison of rand() and mt_rand(). It effectively draws a graph showing how the last generated number affects the next by plotting the numbers in consecutive pairs against each other.

<?php
header
("Content-type: image/png");
$sizex=800;
$sizey=800;

$img imagecreatetruecolor($sizex,$sizey);
$black imagecolorallocate($img,000);
imagefilledrectangle($img00$sizex$sizeyimagecolorallocate($img255255255));

$p 0;
for(
$i=0$i 100000$i++) {
   
$np rand(0,$sizex);
   
imagesetpixel($img$p$np$black);
   
$p $np;
}

$p 0;
for(
$i=0$i 100000$i++) {
   
$np mt_rand(0,$sizex);
   
imagesetpixel($img$p $sizex$np$black);
   
$p $np;
}

imagepng($img);
imagedestroy($img);
?>
2013-01-30 00:56:42
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Автор:
Another generic random string function, but very small and fast.

<?php
function mt_rand_str ($l$c 'abcdefghijklmnopqrstuvwxyz1234567890') {
    for (
$s ''$cl strlen($c)-1$i 0$i $l$s .= $c[mt_rand(0$cl)], ++$i);
    return 
$s;
}

echo 
mt_rand_str(8); // Something like mp2tmpsw
echo mt_rand_str(6'0123456789ABCDEF'); // Something like B9CD0F
?>
2013-08-02 21:05:21
http://php5.kiev.ua/manual/ru/function.mt-rand.html
/dev/urandom provides high entropy, but it is important to remember that it is created by collecting random os garbage from memory - if not enough of that garbage is created reading the file will just block the whole process until there is enough entropy to generate the requested random bytes. in debian-based setups, the rng-tools package can be used to manage entropy.
2013-09-13 23:21:18
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Автор:
To reiterate the message about *not* using mt_rand() for anything security related, here's a new tool that has been just posted that recovers the seed value given a single mt_rand() output:

http://www.openwall.com/php_mt_seed/README
2013-11-05 13:13:32
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Ever wanted a crypto safe mt_rand()? Not useful for many things I guess (maybe not useful at all), but I recently wanted to build a class able to pick random words from a dictionary in a safe way, so they could be used as passwords. I probably overdid it... The result is my attempt on a "cryptographically secure" mt_rand implementation including a wrapper for selecting and using the best random bytes generator from available extensions and /dev/urandom (about 100 times slower than mt_rand on a single core, by the way, so it's clearly open for improvement if you want to fork it on github.com/elcodedocle/cryptosecureprng, where you can find the docs to it too). Here is the minimized version (note too long):
<?php
/**
 * Crypto Secure PRNG
 * @copyright  2014 elcodedocle
 */
class CryptoSecurePRNG {
    private 
$intByteCount 4;
    private 
$defaultMax 2147483647;
    private 
$mcrypt;
    private 
$openssl;
    private 
$urandomFileHandler false;
    public function 
getRandomBytesString($byteCount){
       
$chars '';
        if (
$this->mcrypt) {
           
$chars mcrypt_create_iv($byteCountMCRYPT_DEV_URANDOM);
        }
        if (!
$chars && $this->openssl) {
           
$chars openssl_random_pseudo_bytes($byteCount);
        }
        if (!
$chars && is_resource($this->urandomFileHandler)) {
            while ((
$len  strlen($chars))< $byteCount) {
               
$chars .= fread($this->urandomFileHandler$byteCount $len);
            }
        }
        if (
$len strlen($chars) < $byteCount) {
            for (
$i=0;$i<$len;$i++) { $chars[$i] = $chars[$i] ^ chr(mt_rand(0255)); }
            for (
$i $len$i $byteCount$i++) {
               
$chars .= chr(mt_rand(0255));
            }
        }
        return 
$chars;
    }
    public function 
rand($min 0$max null){
        if (
$max === null) { $max $this->defaultMax; }
        if (!
is_int($min)||!is_int($max)) { throw new Exception('$min and $max must be integers'); }
        if (
$min>$max) { throw new Exception('$min must be <= $max'); }
       
$chars $this->getRandomBytesString($this->intByteCount);
       
$n 0;
        for (
$i=0;$i<strlen($chars);$i++) {$n|=(ord($chars[$i])<<(8*(strlen($chars)-$i-1)));}
        return (
abs($n)%($max-$min+1))+$min;
    }
    public function 
__construct(){
       
$this->mcrypt  function_exists('mcrypt_create_iv');
       
$this->openssl function_exists('openssl_random_pseudo_bytes');
        if (
is_readable('/dev/urandom')){ $this->urandomFileHandler fopen('/dev/urandom''r'); }
    }
    public function 
__destruct(){ 
        if (
is_resource($this->urandomFileHandler )) fclose($this->urandomFileHandler);
    }


$randGen = new CryptoSecurePRNG();
echo 
$randGen->rand();  //outputs rand int between 0 and 2^32
2014-04-22 21:00:12
http://php5.kiev.ua/manual/ru/function.mt-rand.html
I wrote another function to get a random float, if its not precise enougth jut add some '0' to the $mul parameter.

<?php

function f_rand($min=0,$max=1,$mul=1000000){
    if (
$min>$max) return false;
    return 
mt_rand($min*$mul,$max*$mul)/$mul;
}
?>
I made following  tests:
<?php
   
echo f_rand()."<br>";              //0.497153
   
echo f_rand(0.5)."<br>";           //0.857822
   
echo f_rand(0.5,0.6)."<br>";       //0.599956
   
echo f_rand(0,10)."<br>";          //5.801949
   
echo f_rand(0,2,2)."<br>";         //1.5
   
echo f_rand(0,2,10)."<br>";        //1.7
?>
2014-07-12 18:34:09
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Автор:
With PHP 5.3.3, we're seeing odd behavior on 32 bit Linux.

This works fine on 64 bit Linux: 
<?php
printf 
("%08x\n"mt_rand (00xFFFFFFFF));
?>
but on our 32 bit Linux development server, it's always yielding "00000000". 

On that same machine, this: 
<?php
printf 
("%08x\n"mt_rand (00xFFFFFFF0));
?> 
seems to always yield either 00000000 or a number in the range fffffff2 to ffffffff. This: 
<?php
printf 
("%08x\n"mt_rand (00xFFFFFF00));
?> 
gives numbers where the last two digits vary, and so on through at least 0xF0000000. 

However, this: 
<?php
printf 
("%08x\n"mt_rand (00x7FFFFFFF));
?>
seems to be well-behaved.

The moral? On 32 bit systems, be careful about crossing the signed number boundary, 0x7FFFFFFF.
2014-09-13 01:12:49
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Автор:
mt_rand is not calculated by Mersenne Twister.

https://github.com/php/php-src/commit/a0724d30817600540946b41e40f4cfc2a0c30f80
2016-02-19 19:18:08
http://php5.kiev.ua/manual/ru/function.mt-rand.html
rand() comes from the libc, and mt_rand() is internal to PHP. So the differences vary with their respective versions.

On a 64b Debian Stretch with PHP 5.6.21, there is no visible difference: http://oi64.tinypic.com/2nkqas6.jpg

This image compares the two functions. In the top half with random points, in the lower half with random intensity on each point. This is totally different from what was obtained 4 years ago in another note, with an unknown environment.

Here is the code for this visual comparison.
<?php
$sizex 
400;
$sizey 400;

$img imagecreatetruecolor($sizex$sizey);
$white imagecolorallocate($img255255255);
$inks array_map(
    function(
$r) use($img) { return imagecolorallocate($img$r$r$r); },
   
range(0255)
);
for (
$x $x $sizex $x++) {
    for (
$y $y $sizey $y++) {
       
// placing ($sizex x $sizey) white points at random in the top half
       
imagesetpixel($imgrand(0$sizex 1), rand(0$sizey 1), $white);
       
imagesetpixel($img$sizex mt_rand(0$sizex 1), mt_rand(0$sizey 1), $white);
       
// random intensity for each point in the lower half
       
imagesetpixel($img$x$sizey $y$inks[rand(0255)]);
       
imagesetpixel($img$sizex $x$sizey $y$inks[mt_rand(0255)]);
    }
}
header("Content-type: image/png");
imagepng($img);
?>
2016-06-03 13:49:22
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Автор:
Generate random number by Array weights.
Implementation of Vose's Alias Method (http://www.keithschwarz.com/darts-dice-coins/)

<?php
function random_aliasMethod($weight, &$prob = array(), &$alias = array())
{
   
$count count($weight);

    if (empty(
$prob)) {
       
$small = array(); $large = array();
       
$sum array_sum($weight);

        foreach (
$weight as $i => &$w)
            (
$w *= $count $sum) < $small[] = $i $large[] = $i;
        unset(
$w);

        while (!empty(
$small) AND !empty($large)) {
           
$l array_pop($small);
           
$g array_pop($large);
           
$prob[$l] = $weight[$l];
           
$alias[$l] = $g;
            (
$weight[$g] += $weight[$l] - 1) < $small[] = $g $large[] = $g;
        }

        foreach (
$large as $i)
           
$prob[$i] = 1;

        foreach (
$small as $i)
           
$prob[$i] = 1;
    }

    return 
mt_rand() / mt_getrandmax() <= $prob[$i mt_rand(0$count 1)] ? $i $alias[$i];
}

// Example:
$weight = array(012345678910100);
$result random_aliasMethod($weight);

// Distribution test:
$prob = array(); $alias = array(); // for cache
$results array_fill(0count($weight), 0);
for(
$i 0$i 10000; ++$i) {
   
$results[random_aliasMethod($weight$prob$alias)]++;
}
print_r($results);
/*
    [0] => 0
    [1] => 70
    [2] => 136
    [3] => 190
    [4] => 250
    [5] => 322
    [6] => 401
    [7] => 444
    [8] => 492
    [9] => 596
    [10] => 627
    [11] => 6472
*/
2016-09-24 16:46:40
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Though you might all know this, by now: nonetheless, for 'slow- coaches', such as myself; Remember that mt_rand(), reacts DIFFERENTLY, Depending on your (initial) PHP script declaration.

For People, such as myself, who have embraced strict-type; if your script is set to "declare(strict_types=1)", at the top of the page (just after opening PHP tag),  remember one rule of thumb: 

If you pass a FLOAT into mt_rand WITHOUT strict-type set to 1, you should be good to go. However, if you HAVE set strict-types to 1, PHP WILL throw an exception:- "mt_rand() expects parameter 1 to be integer, float given". 

Just so that you don't have to spend a whole hour (like I did), trying to figure out why a script (with mt_rand()) that was working in a separate environment, isn't working now.
2017-08-23 18:55:57
http://php5.kiev.ua/manual/ru/function.mt-rand.html
Автор:
The seed is the PID + LCG (https://github.com/php/php-src/search?q=GENERATE_SEED&unscoped_q=GENERATE_SEED)
2018-12-20 10:24:09
http://php5.kiev.ua/manual/ru/function.mt-rand.html

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