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Unique Random Values I

If you ever needed to get 3 random values off an array in PHP, you'd probably have no problems doing that. But what if your array contained duplicate key and/or value pairs and you still needed to get random yet unique, values?

Sample array with duplicate values

Here's my $sites array filled up with some dummy data to help me explain this problem I faced:

php:



<?php

$sites = array( 'one', 'two', 'two', 'three',
  'three', 'three', 'four', 'four', 'four',
  'four', 'five', 'five', 'five', 'five',
  'five', 'six', 'six', 'six', 'six', 'six',
  'six', 'seven', 'seven', 'seven', 'seven',
  'seven', 'seven', 'seven', 'eight', 'eight',
  'eight', 'eight', 'eight', 'eight', 'eight',
  'eight' );

?>

Now all I needed to get done was to somehow get the script to randomly grab 3 unique 'sites' off this array. Easy enough? Yes, quite but it gets complicated in the end! Anyway, here's my first attempt at the code:

Searching an array randomly and return 3 unique values - Method I

Using the popular PHP for loop, here's what I did in the beginning.

php:



<?php
// continued from the code above

for( $i=0; $i<3; $i++ ) // just get 3 diff. sites
{
  $r = mt_rand( 0, sizeof($sites)-1 ); // generate random key

  //  METHOD I
  //  ========
  if( isset($trio) ) # var $trio will hold the lucky 3 sites
  {
    $c = get_unique( $sites["$r"], $trio ); # function below
    if( $c )
    {
      $trio[] = $c;
    }
    else
    {
      --$i;
    }
  }
  else
  {
    $trio[] = $sites["$r"];
  }
  //  END of METHOD I
  //  ===============
}

// The function needed for Method I to work
function get_unique( $newsite, $trio )
{
  for( $i=0; $i<sizeof($trio); $i++ )
  {
    if( $newsite === $trio[$i] )
    {
      return false; // a duplicate site
    }
  }
  return $newsite; // a unique site
}

?>

Now the variable $trio will be filled-up with 3 random and unique values each time you run this script - good... but not quite! :O

Before I tell you what I found out eventually, I want to show you another method I worked out (which does the same thing):

Part II.

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