Array from Arrays - php

Question

I have the following array:
$learners=array('Eliza'=87, 'Joe'=81, 'Anne'=69, 'Marley'=39, 'Teddy'=39, 'Jemma'=90, 'Sylvia'=87);
So far I have been able to separate the two arrays as follows:
$tudents=array_keys($learners);
$scores=array_values($learners);
The ranking is as follows:
Student Score Position
Jemma 90 1
Sylvia 87 2
Eliza 87 2
Joe 81 4
Anne 69 5
Marley 39 7
Teddy 69 7
I would like to create a new array with names as keys and positions as values i.e
$positions=array('Jemma'=1, 'Sylvia'=2, 'Eliza'=2, 'Joe'=4, 'Anne'=5, 'Marley'=7, 'Teddy'=7);
This will allow me to echo any name and position at any point on the script. I am not sure how to proceed.
The ranking is not straightforward if the scores have duplicates. If there is a tie at number 2, the 3rd position is skipped. If the tie occurs at the end of the scores, then both scores will be placed at the last position and the preceding position will be skipped, in the example above, position 6 has been skipped and the two 39s occupy position 7.
Any help will be appreciated

Answer 1

// Sort decending
arsort($data);
$vals = array_values($data);
$last = end($vals); // The lowest score
$prev = null;
$rank = 0;
$positions = array();
foreach($data as $student => $score) {
if ($score == $last) {
// The score is the same as the lowest, the rank is set to last position
$rank = count($data);
} else if ($prev != $score) {
// We only update if the score is not the same as prev
$rank++;
} else if ($prev == $score) {
// We matched on the key, replace any items with the
// same score with the current rank
$matches = array_keys($positions, $score);
foreach($matches as $key) {
$positions[$key] = $rank;
}
$positions[$student] = $rank;
// Now skip ahead to the next rank +1
$rank = $rank + count($matches) + 1;
continue;
}
$positions[$student] = $rank;
$prev = $score; // Remember the previous score
}
var_dump($positions);

Answer 2

Here's another solution:
First sort by value (the print_r is just to check progress).
arsort($learners);
print_r($learners);
Then make an array of rankings, but don't advance the rank if the score is the same as the previous element's score.
$rank = $pos = 1;
$prev_score = current($learners);
foreach ($learners as $name => $score) {
if ($score != $prev_score) {
$rank = $pos;
}
$ranking[$name] = $rank;
$prev_score = $score;
$pos++;
}
print_r($ranking);
Now correct the last entries, any element with the same score as the last element should be in 7th place. There's a rarely-used argument to array_keys() that searches for a given value.
$low_score = end($learners);
$last_place = count($learners);
foreach (array_keys($learners, $low_score) as $name) {
$ranking[$name] = $last_place;
}
print_r($ranking);
Output:
Array
(
[Jemma] => 90
[Sylvia] => 87
[Eliza] => 87
[Joe] => 81
[Anne] => 69
[Marley] => 39
[Teddy] => 39
)
Array
(
[Jemma] => 1
[Sylvia] => 2
[Eliza] => 2
[Joe] => 4
[Anne] => 5
[Marley] => 6
[Teddy] => 6
)
Array
(
[Jemma] => 1
[Sylvia] => 2
[Eliza] => 2
[Joe] => 4
[Anne] => 5
[Marley] => 7
[Teddy] => 7
)

Answer 3

Looks like PHP, right?
Basically go through your initial list and stuff them into a new array that uses the names as keys (you're in trouble here if two people have the same name, but I'm assuming this is a homework assignment and that's not an issue?)
$sorted = array();
for ($i=0;$i<count($positions);$i++) {
if (!isset($sorted[$positions[$i]["Student"]])) {
$sorted[$positions[$i]["Student"]] = $positions[$i]["Score"];
} else if ($sorted[$positions[$i]["Student"]]<$positions[$i]["Score"] {
$sorted[$positions[$i]["Student"]] = $positions[$i]["Score"];
}
}
What you're doing here is making an array where the KEY is the name of the student, and putting the first score you find in as the VALUE for that. So $sorted["Jemma"] = 90. Then if you hit that name again, and the score is higher than the current value for $sorted["Jemma"], you're replacing it.
After that, you run an arsort($sorted) to put it in order.