以数学方式添加两个多维数组的最有效方法？

Question

Consider two simple arrays:

<?php
  $array1 = array(
    'blue' => 5,

    'green' => array(
      'square' => 10,
      'sphere' => 0.5,
      'triangle' => 3
    ),

    'red' => array(
      'circle' => 1000,
    ),

    'black' => 4,

  );

  $array2 = array(
    'blue' => 1,

    'green' => array(
       'square' => 11,
       'circle' => 5,
    ),

    'purple' => 10,

    'yellow' => array(
      'triangle' => 4
    ),

    'black' => array(
      'circle' => 6,
    ),

  );

I need to mathmatically add together in a recursive way, each value from each $array1 and $array2 .

• Preserve keys
• Where a key does not exist in $array1 but does exist in $array2 , the final array would simply contain the value of $array2 (and the other way around as well)
• Where they exist in both, the numeric values would be added +
• Non-numeric values wouldn't be touched
• If a value on $array1 points to another sub-array, and in $array2 it points to a value, the end value would result in that key containing a subarray that contains the values from $array1 plus a new key/value using the parent name and it's value (see black in the example)
• Should be able to work at virtually unlimited nesting

To clarify, eg if we said

<?php 
  $final = array_merge_special($array1, $array2);

  // We would end up with, if you var_export()'d final, something like:
  // (Note: Hope I didn't make mistakes in this or it will be confusing,
  // so expect mild human error)

  $final = array(
    'blue' => 6, // 5+1

    'green' => array(
      'square' => 21, // (10+11)
      'sphere' => 0.5, // only in $array1
      'triangle' => 3 // only in $array1
      'circle' => 5, // only in $array2
    ),

    'purple' => 10, // only in $array2

    'yellow' => array( // only in $array2
      'triangle' => 4
    ),

    'red' => array( // only in $array1
      'circle' => 1000,
    ),

    'black' => array(
      'circle' => 6, // untouched, while $black is present in both, the $array1 value does not have a 'circle' key, and is actually only a key/value (see below)
      'black' => 4, // the key/value from $array1 that was not a subarray, even though it was a subarray in $array2
    ),

  );

This seems outragously daunting to me. I know I could loop over one array and get easily recursively add the values, and I have this working (somewhat), but it's when I get into special rules (such as ones for black ) that I can't even imagine how broken code would look. There has to be a way to do this would looping over each array individually and unset() 'ing values to merge?

Answer 1

You would use array_walk_recursive (see: See php Manual here ) and possibly array_merge_recursive. I'd have to think it through further to get the full picture.

OK, decided that this wouldn't work! Array_walk_recursive doesn't pass keys that hold arrays to the function. This problem kept flowing aroung in my brain, so I just had to write a function to do it! Here it is:

function dosum($arin) {
  $arout = array();
  foreach ($arin as $key1 => $item1) {
    $total = 0;
    if(is_array($item1)) {
      foreach($item1 as $key2 => $item2) {
        if(is_numeric($key2))
          $total += $item2;
        else
          if(is_array($item2))
            $arout[$key1] = dosum(array($key2 => $item2));
          else
            $arout[$key1][$key2] =$item2;
      }
      if($total)
        if(isset($arout[$key1]))
          $arout[$key1][$key1] = $total;
        else
          $arout[$key1] = $total;
      }
    else
      $arout[$key1] = $item1;    
    }
  return $arout;
  }

For the 2 arrays given, you would use it like this:

print_r(dosum(array_merge_recursive($array1, $array2)));