Array diff of specific key within multi-dimensional array

Question

I have two arrays of products, both formatted exactly the same, like so:

$products = array(
    [0] => array(
        ['product_id'] => 33
        ['variation_id'] => 0
        ['product_price'] => 500.00
    ),
    [1] => array(
        ['product_id'] => 48
        ['variation_id'] => 0
        ['product_price'] => 600.00
    ),
)

I would like to be able to return a list of only those products not found in the second array, based on the product ID.

I only care about those NOT found in the second array, not additional ones added to the first, so array_diff won't seem to do the trick.

what is the functional difference between additional ones added to the first and those not found in the second? are either of the posted solutions doing what you want, or are you looking for something else? — user410344
– user410344, Commented Aug 17, 2010 at 19:33

Brandon Horsley · Accepted Answer · 2010-08-17 19:16:04Z

10

I suspect you want something like array_udiff. This lets you specify how to compare the two arrays, using a callback function. You just create a callback that compares based on product id's.

I think this satisfies what you want because the array_diff family of functions only compare the first array to the rest, it does not return elements that array2 (or 3, or 4) have that array1 does not.

<?php
$products = array(
    0 => array(
        'product_id' => 33,
        'variation_id' => 0,
        'product_price' => 500.00
    ),
    1 => array(
        'product_id' => 48,
        'variation_id' => 0,
        'product_price' => 600.00
    )
);

$products2 = array(
    1 => array(
        'product_id' => 48,
        'variation_id' => 0,
        'product_price' => 600.00
    ),
    2 => array(
        'product_id' => 49,
        'variation_id' => 0,
        'product_price' => 600.00
    )
);

function compare_ids($a, $b)
{
  return $b['product_id'] - $a['product_id'];
}

var_dump(array_udiff($products, $products2, "compare_ids"));
?>

Outputs:

array(1) {
  [0]=>
  array(3) {
    ["product_id"]=>
    int(33)
    ["variation_id"]=>
    int(0)
    ["product_price"]=>
    float(500)
  }
}

edited Aug 17, 2010 at 19:16

answered Aug 17, 2010 at 19:08

Brandon Horsley

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1 Comment

Valentin Despa Over a year ago

Special attention should be paid to make sure you compare arrays with an identical structure. Comparing $b['productID'] with $a['product_id'] will fail.

Freyja · Accepted Answer · 2010-08-17 19:46:50Z

A simple foreach loop should be enough:

<?php
$products = array(
    0 => array(
        'product_id' => 33,
        'variation_id' => 0,
        'product_price' => 500.00
    ),
    1 => array(
        'product_id' => 48,
        'variation_id' => 0,
        'product_price' => 600.00
    )
);

$products2 = array(
    1 => array(
        'product_id' => 48,
        'variation_id' => 0,
        'product_price' => 600.00
    ),
    2 => array(
        'product_id' => 49,
        'variation_id' => 0,
        'product_price' => 600.00
    )
);

$diff = array();

// Loop through all elements of the first array
foreach($products2 as $value)
{
  // Loop through all elements of the second loop
  // If any matches to the current element are found,
  // they skip that element
  foreach($products as $value2)
  {
    if($value['product_id'] == $value2['product_id'])
    continue 2;
  }
  // If no matches were found, append it to $diff
  $diff[] = $value;
}

The $diff array would then only hold the following value:

array (
  0 => 
  array (
    'product_id' => 49,
    'variation_id' => 0,
    'product_price' => 600,
  ),
)

Hope this helped!

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