Comparing Two Arrays for Two Values

Question

I'm struggling with the appropriate logic to compare the following arrays:

$a = [
    "ip" => [
        "1.2.3.4",
        "4.3.2.1",
    ],
    "domain" => [
        "example.com",
        "another.domain",
    ],

];

$b = [
    [
        "id"=> 136589,
        "metaname" => "ip",
        "metavalue" => "1.2.3.4",
    ],
    [
        "id"=> 136590,
        "metaname" => "domain",
        "metavalue" => "example.com",
    ],
];

I need to loop over $a to find the key ('ip') value ('1.2.3.4') combinations that do not exist in $b. In the array $a, I need to capture the ip '4.3.2.1' and the domain 'another.domain'

It is possible for $b to have matching values with different keys?

A good example is that of 'ip' addresses. Possible IP-related metaname values are 'ip', 'ip.dst' and 'ip.src'. Back to the sample data - even if the 'ip' matches, if the metaname does not match it should be skipped.

foreach ($a as $metaName => $metaValues)
{
    foreach ($metaValues as $metaValue)
    {
        foreach ($b as $row)
        {
            if (in_array($metaName, $row) && in_array($metaValue, $row))
            {
                # this pair exists, move on to next $metaName-$metaValue pair
                break;
            }
            # this is where i am now, making small progress
            # more trial and error going on
        }
    }
}

In my sample code the comment is where I need help. I've tried various iterations of different checks and loops to capture the appropriate data to no avail...

• in_array($metaValue, $row)
• array_keys($row, $metaValue)

combined with various if statements and so on but that won't help.

In the event that my description failed to be clear maybe the following table will help.

+ A ---------------------+----+ B ------------------+ Comment ------------------------+
| ip, 1.2.3.4            | == | ip, 1.2.3.4         | Skip, no more checks            |
+------------------------+----+---------------------+---------------------------------+
| ip, 4.3.2.1            | != | ip, 1.2.3.4         | Keep checking                   |
|                        | != | domain, example.com | No more B to compare, I want A! |
+------------------------+----+---------------------+---------------------------------+
| domain, example.com    | != | ip, 1.2.3.4         | Keep checking                   |
|                        | == | domain, example.com | Skip, no more checks            |
+------------------------+----+---------------------+---------------------------------+
| domain, another.domain | != | ip, 1.2.3.4         | Keep checking                   |
|                        | != | domain, example.com | No more B to compare, I want A! | 
+------------------------+----+---------------------+---------------------------------+

Answer 1

With just a slight modification and the use of a reference you are pretty close. But be careful with the first foreach, the first argument is a $metaname, but the second is not yet the $metavalue, you need a second foreach to loop over them:

foreach ($a as $metaname => &$group) { // & is present to unset the original array
    foreach ($group as $i => $metavalue) { // here you get the distinct metavalues
        foreach ($b as $row) {
            if (!($row['metaname'] === $metaname)) {
                continue;
            }
            if ($row['metavalue'] === $metavalue) {
                unset($group[$i]);
            }
        }
    }
}

var_dump($a);

a var_dump() of $a afterwards

array(2) {
  ["ip"]=>
  array(1) {
    [1]=>
    string(7) "4.3.2.1"
  }
  ["domain"]=>
  &array(1) {
    [1]=>
    string(14) "another.domain"
  }
}

---

The first foreach() would access the distinct values of $a arrays whereas $metavalue is in fact the array containing those metavalues.