Question

<?php 
    $c = count($rank); // 5

    for ($i = 0; $i < $c; $i++) {
        $labels [] = array("value" =>$i, "text" => $i);
    }

?>

output: `[{"value":1,"text":1},{"value":2,"text":2},{"value":3,"text":3},{"value":4,"text":4},{"value":5,"text":5}]`

But what I need is:

[{"value":5,"text":1},{"value":4,"text":2},{"value":3,"text":3},{"value":2,"text":4},{"value":1,"text":5}]

Any idea about that?

Answer 1

I’ll describe my line of thinking.

What is the pattern in the sequence 5, 4, 3, 2, 1? Quite clearly, I decrease by one each time. I already know that $i increases by one each time, because that is how we wrote our for loop. My goal and what is available with $i is fairly close, so is there any way I can use $i?

Indeed there is. Instead of saying the sequence 5, 4, 3, 2, 1 decreases by one each time, I can say that the sequence increases in its distance from 5 by one each time. That is, the sequence is equivalent to 5 - 0, 5 - 1, 5 - 2, 5 - 3, 5 - 4. Notice that this lines up perfectly with $i. Therefore, our solution can be the following:

<?php 
$c = count($rank); // 5

for ($i = 0; $i < $c; $i++) {
      $labels [] = array("value" =>($c - $i), "text" => $i);
}

This takes a bit of intuition to see, and if you are in a similar situation and cannot figure out the pattern, you can always introduce a new variable.

<?php 
$c = count($rank); // 5


for ($decreasing = $c, $i = 0; $i < $c; $i++, --$decreasing) {
      $labels [] = array("value" =>$decreasing, "text" => $i);
}