How to create random hexadecimal number of X digits?

I have always liked this solution, it may use a not so orthodox method, but it has worked for me, it is simple and short:

substr(md5(rand()), 0, 5);

You can enter a range of values ​​in rand()if you wish.

I have created the following function, which receives as a parameter the number of digits that the hexadecimal code must have.

    <?php

function hexadecimalAzar($caracteres){

    $caracteresPosibles = "0123456789abcdef";
    $azar = '';

    for($i=0; $i<$caracteres; $i++){

        $azar .= $caracteresPosibles[rand(0,strlen($caracteresPosibles)-1)];

    }

    return $azar;

}

echo hexadecimalAzar(5);

For an even number of characters, something short:

function hexadecimalAzar($caracteres){
    $bytes = random_bytes($caracteres/2);
    return bin2hex($bytes);
}

For the most general case, you would have to write some more code.

Edited :

...and the general case:

function hexadecimalAzar($caracteres){
    $bytes = random_bytes($caracteres/2 + 1);
    return substr(bin2hex($bytes), 0, $caracteres);
}

With Php7 I would do it like this:

function decimal_hex ():string
    {
      $n = dechex(rand(1, 100));

      return $n;
    }


    echo decimal_hex();

Since Php has a native function to convert a decimal to hexadecimal ( link documentation ), you simply get a random decimal and convert it to hexadecimal.

If you want n values, you call the function inside a loop:

 $n = 100;
    while ($n)
    {
      echo decimal_hex() . '</br>';
      $n--;
    }

But it's up to you how to use the function. It can still be like this:

function decimal_hex ():string
  {
    return dechex(rand(1, 100));
  }

And finally, the :string is a new feature of Php7 with which you indicate the type of return value, in this case string because it can return letters and numbers.

Greetings.