PHP Compare and change certain elements in multidimensional arrays - php

Question

To be short, I have two simple arrays and I want to verify if certain keys from the second array have empty values and replace them with their correspondent values from the first array.
Example:
$a1 = [ 1 => 'one', 2 => 'two', 3 => 'three',5=>'cinco', 6=>'six'];
$a2 = [ 2 => 'two', 5=>'five', 6=>'' ];
Result:
Array
(
[2] => two
[5] => five
[6] => six
)
The following code works already for this.
$keys = array_keys($a1);
foreach ($keys as $k)
{
if ((isset($a2[$k])) && (($a2[$k]) == '')) {
$a2[$k] = $a1[$k];
}
}
print_r($a2);
But what if we want to apply this for two 2D arrays? What will be the proper approach in that case? Let's say these two 2D arrays will be:
$superheroes_complete = array(
"spiderman" => array(
"name" => "Peter Parker",
"email" => "peterparker#mail.com",
),
"superman" => array(
"name" => "Clark Kent",
"email" => "clarkkent#mail.com",
),
"ironman" => array(
"name" => "Harry Potter",
"email" => "harrypotter#mail.com",
)
);
$superheroes_empty = array(
"spiderman" => array(
"name" => "Peter Parker",
"email" => "",
),
"superman" => array(
"name" => "Clark Kent",
"email" => "something",
),
"ironman" => array(
"name" => "Harry Potter",
"email" => "another one",
)
);
Expectation:
$superheroes = array(
"spider-man" => array(
"name" => "Peter Parker",
"email" => "peterparker#mail.com",
),
"super-man" => array(
"name" => "Clark Kent",
"email" => "something",
),
"iron-man" => array(
"name" => "Harry Potter",
"email" => "another one",
)
);
Much appreciation and thank you in advance!

Answer 1

You've added another level to your data, so you can just add another level to your checking as well with a second foreach loop:
foreach ($superheroes_complete as $hero => $info) {
foreach ($info as $key => $value) {
if (empty($superheroes_empty[$hero][$key])) {
$superheroes_empty[$hero][$key] = $value;
}
}
}

Answer 2

First note that your 1D case can be simplified:
foreach ($a2 as $k => $v) {
if (!isset($v)) {
$a2[$k] = $a1[$k];
}
}
Then for the 2D case, assuming the 1st level keys are always the same (or it becomes a quite different question!):
foreach ($superheroes_complete as $main_k => $main_v) {
foreach ($main_v as $k => $v) {
if (!isset($v)) {
$superheroes_empty[$main_k][$k] = $superheroes_complete[$main_k][$k];
}
}

Answer 3

If you only need to take care of the "email" field you can do this :
<?php
$keys = array_keys($superheroes_complete);
foreach ($keys as $k)
{
if ((isset($superheroes_empty[$k]["email"])) &&
(($superheroes_empty[$k]["email"]) == '')) {
$superheroes_empty[$k]["email"] = $superheroes_complete[$k]["email"];
}
}
var_dump($superheroes_empty);
?>

Answer 4

For the generic case where the depth of nesting is unlimited, you could use this recursive function:
function fillEmpty(&$filled, &$empty) { // arguments are by reference
if ($empty === "") {
$empty = $filled;
return;
}
if (!is_array($filled) || !is_array($empty)) return;
foreach ($filled as $key => $value) {
if (isset($empty[$key])) fillEmpty($value, $empty[$key]);
}
}
Example call:
fillEmpty($superheroes_complete, $superheroes_empty);
This modifies the second argument, filling the empty values.
See it run on eval.in

Answer 5

It might be your lucky day, php has some built in functions to compare arrays values and keys. Use array_diff() which can compare two or more arrays and return the difference. You could also use array_intersect() which does the opposite.
If you want to only compare the keys, use array_diff_key()which returns only the key difference or array_intersect_key() which returns the matched keys.

Answer 6

You could also consider a recursive solution. This could work on both the 1D and 2D arrays, or even an array of N dimensions.
I'm aware that recursion should be used with care, as it can be quite resource intensive. This is however a more versatile solution, and keeps the code cleaner with less nested control structures and early returns, which I find better readable. I'll use the native array_walk method because I was taught that it should perform better then a php loop.
So this is what my code would look like:
function array_complement_recursive(&$partial, $complete) {
array_walk($partial, function(&$value, $key) use ($complete) {
// (for safety) complete does not contain matching key: done
if (! array_key_exists($key, $complete)) {
return;
}
// value is array: call recursive
if (is_array($value)) {
array_complement_recursive($value, $complete[$key]);
return;
}
// value is not 'empty': done
// note that null, 0, false will also not match, you may want to make
// this check more specific to match only the empty string
if ($value) {
return;
}
$value = $complete[$key];
});
}
I've set up a little demo so you can see that it works on both your examples. And as I said, it should even work for arrays with more dimensions, or a more irregular structure.
http://phpfiddle.org/main/code/49iz-vrwg
I've added some comments to explain, but feel free to ask if anything is unclear.