如何在php中提取关联数组中的相邻词对？

Question

I have an associative array in PHP like this:

$weight["a"]=1;
$weight["b"]=4;
$weight["c"]=5;
$weight["d"]=9;

Here I want to calculate pair-wise difference between consecutive array elements, e.g.,

"b-a" = 3
"c-b" = 1
"d-c" = 4

How should this be computed?

Answer 1

Try this:
    $i = 0;
    foreach ($weight AS $curr) { 
      if ($i > 0) {
        echo '"'.array_keys($weight)[$i].'-'.array_keys($weight)[$i-1].'" = '.($curr-$prev)."<br />";    
      }
      $i++;
      $prev = $curr;
    }