How can I generate a 7-character alpha-numeric key?

Question

How can I generate a key with 7 alpha-numeric characters, completely random in PHP?

In other words I want to make a key with numbers and uppercase letters completely random.

I’ve tried using Rand, but Rand only generate numbers.

Answer 1

The safest method to generate a pseudo-random combination is by using the random_bytes().

So use as follows:

$numero_de_bytes = 4;

$restultado_bytes = random_bytes($numero_de_bytes);
$resultado_final = bin2hex($restultado_bytes);

This will generate a combination of 8 characters, pseudo-random.

To switch to uppercase use the strtoupper, as strtoupper($resultado final). To remove one of the characters, to make it 7 instead of 8, use the substr(), thus substr($resultado_final, 1).

Resulting in:

$resultado_final = strtoupper(substr(bin2hex(random_bytes(4)), 1));

This function is available in PHP 7 (and above), to use it in older versions see in this implementation.

Answer 2

A while ago I arrived at this function:

function generateRandomString($size = 7){
   $chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuwxyz0123456789";
   $randomString = '';
   for($i = 0; $i < $size; $i = $i+1){
      $randomString .= $chars[mt_rand(0,60)];
   }
   return $randomString;
}

Answer 3

sprintf and mt_rand

Another short and simple option would be matching mt_randwith sprintf.

sprintf('%07X', mt_rand(0, 0xFFFFFFF))

In case I explain:

mt_rand will generate a number of 0 until 0xFFFFFFF (equivalent to an int 268435455).

sprintf format a value according to a specific parameter. I used the modifier case %X, that formats a value for a hexadecimal number (uppercase X means the letters will be uppercase, if you want lowercase you can use %x).However, before the X there is a number 7. This means that the value that will be formatted in the second parameter of sprintf shall contain 7 characters or more. And finally, the 0 before the 7 means that when it is not 7 characters long, it will be filled in with 0.

So, briefly explaining:

'%' - curinga do modificador
`0` - o número a ser preenchido quando faltar
`7` - quantidade especificada para formatação
`X` - formatada para hexadecimal, com letras maiúsculas (pode ser trocado para `x`)

str_shuffle, str_repeat and substr

The function str_shuffle PHP’s purpose is to mix a certain string. With applied intelligence, you can also produce good results through it.

In my example, I created a list of characters from a to z and 0 to 9. I used str_repeat to repeat the character list. Then I used substr to reduce the 7.

Example:

    $ascii = implode('', array_merge(range('a', 'z'), range(0, 9)));

    $ascii = str_repeat($ascii, 5);

    substr(str_shuffle($ascii), 0, 7);

You can also use a function called random_bytes, but you may have to work with value conversions, since the values returned by it are characters that go beyond the alpha-numeric. You can specify through the first parameter how many bytes you want:

     openssl_random_pseudo_bytes(7) // dJ─Å(\x01"

One last option would be to use dechex(mt_rand(0, 0xfffffff))

Answer 4

Here is another alternative to generate a 7-character pseudo-random string, including uppercase, minuscule, and number:

$upper = implode('', range('A', 'Z')); // ABCDEFGHIJKLMNOPQRSTUVWXYZ
$lower = implode('', range('a', 'z')); // abcdefghijklmnopqrstuvwxyzy
$nums = implode('', range(0, 9)); // 0123456789

$alphaNumeric = $upper.$lower.$nums; // ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789
$string = '';
$len = 7; // numero de chars
for($i = 0; $i < $len; $i++) {
    $string .= $alphaNumeric[rand(0, strlen($alphaNumeric) - 1)];
}
echo $string; // ex: q02TAq3

Answer 5

<?php
    function chaveAlfaNumerica($QuantidadeDeCaracteresDaChave){
        $res = implode('', range('A', 'z')); // ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxiz
        $con = 1;
        $var = '';
        while($con < $QuantidadeDeCaracteresDaChave ){
            $n = rand(0, 57); 
            if (($n == 26) || ($n == 27) || ($n == 28) || ($n == 29) || ($n == 30) || ($n == 31)){
        }else{
            $var = $var.$n.$res[$n];
            $con++;
            }
        }
        return substr($var, 0, $QuantidadeDeCaracteresDaChave);
        }
        //chamando a função.
        echo chaveAlfaNumerica(3);
        //retorna a chave com a quantidade passada no parametro.
?>

I created this function that creates a random key in php,