Array diff of specific key within multi-dimensional array - php

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.

Answer 1

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)
}
}

Answer 2

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!