Weighted percentage between two links? - php

Question

I'm working with two rotating links in a php redirector, is there a way to weight them in percentages?
For example: The first link will have a 70% chance or getting redirected and second 30%.
Code:
<?php
$k = $_GET['sub'];
$aff[] = 'http://google.com';
$aff[] = 'http://yahoo.com';
srand ((double) microtime() * 1000000);
$random_number = rand(0,count($aff)-1);
$lol = ($aff[$random_number]);
$lal = $lol.$k;
header("Location: $lal");
?>
There are similar questions but involve more than two variables.

Answer 1

This seems to work.
$array = array(70 => "http://google.com",
30 => "http://yahoo.com");
$random_number = rand(0, 100);
$last_interval = 0;
$link = "";
foreach( $array as $key => $value ) {
// in range?
if($random_number > $last_interval && $random_number < $key + $last_interval) {
$link = $value;
break;
}
$last_interval = $key;
}
echo "You chose: " . $link;
Concept was taken from https://softwareengineering.stackexchange.com/questions/150616/return-random-list-item-by-its-weight and adapted slightly here is a concept that would work. Credit to #Benjamin Kloster who made the original post.
Prepare a list of intervals that cover 0 to sum(weights, 30 and 70 in your case). Each interval represents one link, its length being it's weight, so for your example:
intervals = [70, 100]
Where an index of 0-70 represents link #1, 70-100 link #2.
Generate a random number n in the range of
0 to sum(weights)
Find the interval in which n falls and you got your link.

Answer 2

Maybe you can do it like this:
$array = array(
array( 30, 'http://google.de/' ),
array( 70, 'http://google.com/' )
);
$number = rand( 1, array_sum( array_column( $array, 0 ) ) );
$lastsum = 0;
foreach( $array as $arr ){
if( $number > $lastsum && $number <= ( $lastsum + $arr[0] ) ){
$url = $arr[1];
break;
}
$lastsum += $arr[0];
}