How to Efficently count user's rank by amout of likes? - php

Question

I have an array, that looks like this,
$users = array(
0 => array(
'user_id' => 'user_1',
'likes' => 50,
),
1 => array(
'user_id' => 'user_2',
'likes' => 72
),
2 => array(
'user_id' => 'user_3',
'likes' => 678
)
);
All I want to do is to implement ratings system according to amount of likes, so that it would look like as:
#rank 1 - user_3
#rank 2 - user_2
#rank 3 - user_1
I ended up with,
$user_counter = new User_Counter();
$user_counter->setData($users);
echo $user_counter->fetchRankByLikes(678);
class User_Counter
{
protected $array;
public function setData(array $array)
{
$this->array = $this->sort($array);
}
protected function sort(array $array)
{
$result = array();
foreach ($array as $index => $_array) {
$result[] = $_array['likes'];
}
// This will reset indexes
sort($result, SORT_NUMERIC);
$result = array_reverse($result);
$return = array();
$count = 0;
foreach ($result as $index => $rank) {
$count++;
$return[$count] = $rank;
}
$return = array_unique($return);
return $return;
}
public function getAll()
{
return $this->array;
}
public function fetchRankByLikes($likes)
{
$data = array_flip($this->array);
return $data[$likes];
}
public function fetchLikesByRank($rank)
{
return $this->array[$rank];
}
}
My problem is that, this approach lies sometimes - for example it gives incorrect info when there are no likes at all ( === i.e all members have 0 likes) - in that case it gives first rank to them all.
Is there another efficient approach to count user's rating by amount of their likes?
Or what am I doing wrong in my computations?
Thanks.

Answer 1

If you're looking for efficiency, I would look at the usort() function, native to PHP:
http://us1.php.net/manual/en/function.usort.php
What usort does is take an array and iteratively walk through it, providing an outside function with 2 items from it's input at a time. It then waits for the function to return either 1, -1 or 0 and determines the following truths:
-1 means left < right
+1 means left > right
0 means both parameters are equal
Here's a practical example:
$users = array(
0 => array(
'user_id' => 'user_1',
'likes' => 50,
),
1 => array(
'user_id' => 'user_2',
'likes' => 72
),
2 => array(
'user_id' => 'user_3',
'likes' => 678
)
);
usort($users, "sortLikesAscending");
function sortLikesAscending($a, $b) {
if ($a['likes'] > $b['likes']) {
return 1;
} elseif ($a['likes'] < $b['likes']) {
return -1;
} else {
return 0;
}
}
Hope that helps!
EDIT:
If you want to implement this usort() methodology from inside your User_Counter class, then call usort like this:
// From somewhere inside User_Counter, assumes User_Counter::mySortingFunction() is defined
usort($this->array, array(&$this, "mySortingFunction"));
The function callback is passed as an array with two entries: a &reference to an object containing the function and the function name as a string.