A faster method to create complicate password

Existing method

Have been using the following function to create password for years.

function randpass($passlength = 10) 
{
  $i = 0;
  while($i < $passlength){
      $foo = chr(rand(33,122));
      if(strpos("123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz$_?!.", $foo) === FALSE) continue;
      if(strpos($pass, $foo) !== FALSE ) continue;
      $pass .= $foo;
      $i++;
  }
  return $pass;
}

New method

Recently found that this method is quite slow. A much simpler and faster method.

function random_pass($i=10){
  for($j=33; $j<128; $j++) { $letters[] = chr($j); }  
  shuffle($letters);
  $subset = array_slice($letters, 0, $i);
  return implode('',$subset);
}  

Test output

Here are the results for some kind of benchmark tests:
1. Produce 1M random strings with both methods.
2. Run the test for string length from 8 to 20.

String length	Time of method 1	Time of method 2
8	15.185411930084	2.1637690067291
9	17.162335157394	2.9013810157776
10	19.071127176285	2.9580578804016
11	21.024034976959	2.9672908782959
12	22.92680311203	2.973995923996
13	24.843096017838	3.0049130916595
14	26.952475070953	3.0360279083252
15	28.952363967896	3.0420889854431
16	31.086222887039	3.0596430301666
17	33.311107873917	3.0881309509277
18	35.279084920883	3.142566204071
19	37.746668100357	3.1463310718536
20	40.050843000412	3.1662061214447

Conclusions:

1. The first method used more time in any case.
2. The longer of the string, the more time the first method used.
3. The time used by the second method to produce 1M strings was almost unchanged for different string lengths.