RE: [PHP] creating random strings?

[Sean Malloy]

My comment would be on the readability and portability of the code.... Think
of someone else coming along to look at that! ;)

This is what I would do; create one function, GenerateString(int $length,
int $type)

function GenerateString($length = 6, $type = 1)
{
  $string = '';
  // seed rand function
  list($usec, $sec) = explode(' ', microtime());
  $microtime = ((float)$usec + (float)$sec);
  srand((double) $microtime * 1000000);

  // loop till $length - 1
  for ($i = 0; $i < $length; $i++)
  {
    // its a password, set the choice to be between 1 and 4
    if ($type == 2)
    {
      $choice = rand(1, 4);
    }
    // its a username, set the choice to be between 1 and 2
    else
    { $choice = rand(1, 2); }

    switch ($choice)
    {
      //generate a random number representing ascii character between a-z
      case 1:
      case 2: $min = 97; $max = 122; break;
      //generate a random number representing ascii character between 0-9
      case 3:
      case 4: $min = 48; $max = 57; break;
    }
    // add the character to our string
    $string .= chr(rand($min, $max));
  }
  // return our generated string
  return $string;
}

// for readability
define('L_USER', 1);
define('L_PASS', 2);

//for a username, you want 8 character a - z
$username = GenerateString(8, L_USER);

//for a username, you want 6 character a - z and 0-9
$password = GenerateString(6 L_PASS);


Hope that gives you some alternative ideas to explore


> -----Original Message-----
> From: Paul Chvostek [mailto:[EMAIL PROTECTED]]
> Sent: Friday, 20 December 2002 10:47 AM
> To: [EMAIL PROTECTED]
> Subject: [PHP] creating random strings?
>
>
>
> I need to create batches of randomly generated usernames and passwords.
> To start off, I have:
>
>  $validuchars='abcdefghijkmnopqrstuvwxyz';
>  $validpchars='abcdefghijkmnopqrstuvwxyz23456789';
>  $lenu=strlen($validuchars)-1;
>  $lenp=strlen($validpchars)-1;
>
> The first method I came up with was:
>
>  $uid=''; for($i=8;$i;$i--) $uid.=substr($validchars,mt_rand(0,$lenu),1);
>  $pwd=''; for($i=8;$i;$i--) $pwd.=substr($validchars,mt_rand(0,$lenp),1);
>
> But I'm wondering if there's any significant benefit to this instead:
>
>  for( $uid=''; strlen($uid)<8;
> $uid.=substr($validuchars,mt_rand(0,$lenu),1) );
>  for( $pwd=''; strlen($pwd)<8;
> $pwd.=substr($validpchars,mt_rand(0,$lenp),1) );
>
> I can't see any difference in speed.  Does the savings of the $i variable
> have any signficance at all?
>
> Another thing I was thinking of doing was making more pronouncable
> usernames with something like:
>
>  $cons="bcdfghjklmnpqrstvwxyz";
>  $vowels="aeiouy";
>  $lenv=strlen($vowels)-1;
>  $lenc=strlen($cons)-1;
>  $uid=""; for($i=4;$i;$i--)
>   $uid.=substr($cons,mt_rand(0,$lenc),1) .
> substr($vowels,mt_rand(0,$lenv),1);
>
> Any thoughts?
>
> Incidentally, I'm guaranteeing uniqueness of usernames with a unique
> index in the MySQL table that stores this stuff.  Including the INSERT,
> I can create about 100000 of these in 60 seconds.  So this is more a
> question of style than of practical limitations.  ;)
>
> --
>   Paul Chvostek                                             <[EMAIL PROTECTED]>
>   Operations / Abuse / Whatever                          +1 416 598-0000
>   it.canada - hosting and development                  http://www.it.ca/
>
>
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