Generate 5 character random string php

I want to create exact 5 random characters string with least possibility of getting duplicated. What would be the best way to do it? Thanks.

Tim Cooper

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asked Mar 25, 2011 at 22:26

3

$rand = substr[md5[microtime[]],rand[0,26],5];

Would be my best guess--Unless you're looking for special characters, too:

$seed = str_split['abcdefghijklmnopqrstuvwxyz'
                 .'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
                 .'0123456789!@#$%^&*[]']; // and any other characters
shuffle[$seed]; // probably optional since array_is randomized; this may be redundant
$rand = '';
foreach [array_rand[$seed, 5] as $k] $rand .= $seed[$k];

Example

And, for one based on the clock [fewer collisions since it's incremental]:

function incrementalHash[$len = 5]{
  $charset = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
  $base = strlen[$charset];
  $result = '';

  $now = explode[' ', microtime[]][1];
  while [$now >= $base]{
    $i = $now % $base;
    $result = $charset[$i] . $result;
    $now /= $base;
  }
  return substr[$result, -5];
}

Note: incremental means easier to guess; If you're using this as a salt or a verification token, don't. A salt [now] of "WCWyb" means 5 seconds from now it's "WCWyg"]

answered Mar 25, 2011 at 22:28

Brad ChristieBrad Christie

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6

If for loops are on short supply, here's what I like to use:

$s = substr[str_shuffle[str_repeat["0123456789abcdefghijklmnopqrstuvwxyz", 5]], 0, 5];

answered Mar 26, 2011 at 0:34

MatthewMatthew

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7

A speedy way is to use the most volatile characters of the uniqid function.

For example:

$rand = substr[uniqid['', true], -5];

answered Mar 25, 2011 at 22:40

John ParkerJohn Parker

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2

You can try it simply like this:

$length = 5;

$randomletter = substr[str_shuffle["abcdefghijklmnopqrstuvwxyz"], 0, $length];

more details: //forum.arnlweb.com/viewtopic.php?f=7&t=25

clami219

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answered Jun 29, 2016 at 22:25

0

The following should provide the least chance of duplication [you might want to replace mt_rand[] with a better random number source e.g. from /dev/*random or from GUIDs]:

EDIT:
If you are concerned about security, really, do not use rand[] or mt_rand[], and verify that your random data device is actually a device generating random data, not a regular file or something predictable like /dev/zero. mt_rand[] considered harmful:
//spideroak.com/blog/20121205114003-exploit-information-leaks-in-random-numbers-from-python-ruby-and-php

EDIT: If you have OpenSSL support in PHP, you could use openssl_random_pseudo_bytes[]:

answered Mar 26, 2011 at 0:32

ArcArc

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3

I always use the same function for this, usually to generate passwords. It's easy to use and useful.

function randPass[$length, $strength=8] {
    $vowels = 'aeuy';
    $consonants = 'bdghjmnpqrstvz';
    if [$strength >= 1] {
        $consonants .= 'BDGHJLMNPQRSTVWXZ';
    }
    if [$strength >= 2] {
        $vowels .= "AEUY";
    }
    if [$strength >= 4] {
        $consonants .= '23456789';
    }
    if [$strength >= 8] {
        $consonants .= '@#$%';
    }

    $password = '';
    $alt = time[] % 2;
    for [$i = 0; $i < $length; $i++] {
        if [$alt == 1] {
            $password .= $consonants[[rand[] % strlen[$consonants]]];
            $alt = 0;
        } else {
            $password .= $vowels[[rand[] % strlen[$vowels]]];
            $alt = 1;
        }
    }
    return $password;
}

answered Mar 25, 2011 at 22:36

1

It seems like str_shuffle would be a good use for this. Seed the shuffle with whichever characters you want.

$my_rand_strng = substr[str_shuffle["ABCDEFGHIJKLMNOPQRSTUVWXYZ"], -5];

answered Sep 12, 2016 at 16:08

1

I also did not know how to do this until I thought of using PHP array's. And I am pretty sure this is the simplest way of generating a random string or number with array's. The code:

function randstr [$len=10, $abc="aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpPqQrRsStTuUvVwWxXyYzZ0123456789"] {
    $letters = str_split[$abc];
    $str = "";
    for [$i=0; $i= PHP 5.5] function is
doing the job for generation of decently long set of uppercase and lowercase characters and numbers. 
Two concat. strings before and after password_hash within $random function are suitable for change. 
Paramteres for $random[] *[$a,$b] are actually substr[] parameters. :]
NOTE: this doesn't need to be a function, it can be normal variable as well .. as one nasty singleliner, like this:
$random=[substr[str_shuffle[['\\`]/|@'.password_hash[mt_rand[0,999999], PASSWORD_DEFAULT].'!*^&~[']], 0, 5]];

echo[$random];
 answered Dec 24, 2015
at 13:10
 
SpookySpooky
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function CaracteresAleatorios[ $Tamanno, $Opciones] {
    $Opciones = empty[$Opciones] ? array[0, 1, 2] : $Opciones;
    $Tamanno = empty[$Tamanno] ? 16 : $Tamanno;
    $Caracteres=array["0123456789","abcdefghijklmnopqrstuvwxyz","ABCDEFGHIJKLMNOPQRSTUVWXYZ"];
    $Caracteres= implode["",array_intersect_key[$Caracteres, array_flip[$Opciones]]];
    $CantidadCaracteres=strlen[$Caracteres]-1;
    $CaracteresAleatorios='';
    for [$k = 0; $k < $Tamanno; $k++] {
        $CaracteresAleatorios.=$Caracteres[rand[0, $CantidadCaracteres]];
    }
    return $CaracteresAleatorios;
}
 
Tom

  

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 answered Mar 24, 2017 at 15:23

1
I`ve aways use this:

When you call it, sets the lenght of string.

You can also change the possible characters in the string $a.
 answered May 11, 2016 at 4:03
 
LipESprYLipESprY
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1
Simple one liner which includes special characters:
echo implode["", array_map[function[] {return chr[mt_rand[33,126]];}, array_fill[0,5,null]]];
Basically, it fills an array with length 5 with null values and replaces each value with a random symbol from
the ascii-range and as the last, it joins them together t a string.
Use the 2nd array_fill parameter to control the length.
It uses the ASCII Table range of 33 to 126 which includes the following characters:
!"#$%&'[]*+,-./0123456789:;?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
 answered Jan 31 at 16:02
 

CodeBrauerCodeBrauer
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