0

I need to create a auto incrementing string similar to this randomly via php. The string is like this. So what i need is a mix of numbers and letter that is randomally generated and doesnt have to be sequential just as long as its random like this 823N9823 and it has 8 characters max

Improve this question
1

6 Answers 6

Reset to default
3

If the characters don't need to be unique:

function randomString($length = 8, $chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789') {
    $randomString = '';
    $numofChars = strlen($chars);
    while (--$length) {
        $randomString .= $chars[mt_rand(0, $numofChars - 1)];
    }
    return $randomString;
}

If the characters must be unique:

function randomString($length = 8, $chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789') {
    return substr(str_shuffle($chars), 0, 8);
}
Improve this answer
Sign up to request clarification or add additional context in comments.

Comments

1

usage: 

echo generateRandomName();

function:

function generateRandomName($length=8,$level=2){

   list($usec, $sec) = explode(' ', microtime());
   srand((float) $sec + ((float) $usec * 100000));

   $validchars[1] = "0123456789abcdfghjkmnpqrstvwxyz";
   $validchars[2] = "0123456789abcdfghjkmnpqrstvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
   $validchars[3] = "0123456789_!@#$%&*()-=+/abcdfghjkmnpqrstvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_!@#$%&*()-=+/";

   $password  = "";
   $counter   = 0;

   while ($counter < $length) {
     $actChar = substr($validchars[$level], rand(0, strlen($validchars[$level])-1), 1);

     // All character must be different
     if (!strstr($password, $actChar)) {
        $password .= $actChar;
        $counter++;
     }
   }

   return $password;

}

Found on PHPToys

Level the level of characters to be used, 3 have special chars as $validchars[3] has.

You also can call it as: generateRandomName(5) to generate a name with length of 5.

Improve this answer

Comments

1 
function generateRandomString($length=8, $characters='abcdefghijklmnopqrstuvwxyz0123456789'){
   $str = '';
   $len = strlen($characters);
   for($i=0; $i<length; $i++){
      $str .= $characters[mt_rand(0, $len)];
   }
   return $string;
}

Usage:

//generates a random string, using defaults: length = 8 and characters = a-z, 0-9
echo "Your password: " . generateRandomString();
//custom length: 10
echo "Thingeys: " . generateRandomString(10);
//digits only, length 4
echo "Your PIN: " . generateRandomString(4, '0123456789');
Improve this answer

Comments

1

You can use mt_rand() to generate a random integer and then transform the values into a string. The function below will give you 2 821 109 907 456 possible values.

function random_id($length = 8) {
  $validChars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';

  $rndString = '';

  for($i = 0; $i < $length; $i++) {
    $rndString .= $validChars[mt_rand(0, strlen($validChars) - 1)];
  }

  return $rndString;
}

$lengthEight = random_id();
$lengthTen = random_id(10);

Since there are more letters and numbers in the list of possible characters, you'll usually get a string with more letters then numbers.

If you want to skew the results towards a string with more numbers then letters, then you can use the following:

function skewed_random_id($numericFactor = 0.8, $length = 8) {
  $validAlpha = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
  $validNumeric = '0123456789';

  $rndString = '';

  for($i = 0; $i < $length; $i++) {
    if((mt_rand() / mt_getrandmax()) < $numericFactor) {
      $rndString .= $validNumeric[mt_rand(0, strlen($validNumeric) - 1)];
    } else {
      $rndString .= $validAlpha[mt_rand(0, strlen($validAlpha) - 1)];
    }
  }

  return $rndString;
}

$eightyPercentNumeric = skewed_random_id();
$fiftyFifty = skewed_random_id(0.5);
$allAlpha = skewed_random_id(0);
$allNumeric = skewed_random_id(1);
Improve this answer

Comments

0 
echo substr(str_replace(array('/', '+'), '', base64_encode(sha1(uniqid(), true))), 0, 8);

Sample output:

LTeQpy9p
v11oy9R7
TjdkXZru
lh3TvNi4
X5Ca0ZXS
L01RfhxW
QDfwNnGO

you can use strtoupper and strtolower to get a version that suits your needs.

EDIT:

If you are gonna use this for something critical rather than just wanting a random string, change uniqid() into mt_rand():

echo substr(str_replace(array('/', '+'), '', base64_encode(sha1(
    mt_rand(). '.'. mt_rand(). '.'. mt_rand()%4 //256^8 of input possibilities (8 bytes)
, true))), 0, 8);
Improve this answer

11 Comments

-1: While this is "random" per-say, the number of collisions you'll get is not even funny. Also, it will contain unwanted characters such as + or /. EDIT: You won't get unwanted characters anymore, but are still limited to a small amount of values...
@Andrew I fixed the / and + before you cast your vote/comment :) and why are you saying that it would be limited to a small amount of values?
Base64 encodes each set of 6 bytes... This means that an 8 character Base64 represents the first 6 characters of the sha1 string 8 * 6b / 8b. 6 sha1 hex chars have 16 777 216 possibilities (16^6) (so 16 777 216 possible Base64 results), which is well below the 2 821 109 907 456 possible values of a properly formatted 8 chars upper-alpha-numeric string (36^8). Actually, if you add lowercases, you get 218 340 105 584 896 possible values for an 8 chars alpha-numeric-string (62^8).
@aularon: Since your function only returns a set of 16 777 216 possible values, it is far from the 2 821 109 907 456 values of the functions located above (actually, it's about 0.0005% of the distributions you'll get above). Also, I didn't take into considerations that uniqid does not provide and infinite number of values, which also limit the set of possible values for the hash, which reduces your number of possible values in the end too. But that would be hard to calculate. mt_rand() does not increase your list of possible values.
@Andrew But I get sha1 as binary, not as hex chars (true as second parameter for sha1 in PHP does so).
|
-1 
substr(uniqid(), 0, 8);

http://php.net/uniqid

Improve this answer

5 Comments

uniqid isn't random. It is quite predictable (You will need to test only some thousand strings if you know the approximate time the string was generated at.)
I think you are forgetting that, regardless, any solution is pseudo-random and thus predictable. Don't down-vote me without knowing what qualities of a RNG John really needs.
Yes, but it is still less predictable. Also, uniqid is limited to hexadecimal values... Therefore, your function can return 4 294 967 296 values... A far cry from the 2 821 109 907 456 possible values of the functions above.
I repeat what I already said. The debate is fine. The down-vote is completely uncalled for.
4 294 967 296 doesn't give you a lot of leg room compared to 2 821 109 907 456 when taking about collisions and nonce. Yes, they are predictable, but a larger chance of collision is not a good thing. Higher collisions is the reason I downvoted.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.