PHP: Update objects array values with another unsorted objects array

Question

I have two objects arrays.

First array $x:

[0] => stdClass Object
    (
        [id] => 54
        [value] => test54
        [something] => testtest54
    )

[1] => stdClass Object
    (
        [id] => 21
        [value] => test21
        [something] => testtest21
    )
...

Second array $y:

[0] => stdClass Object
    (
        [id] => 21
        [value] => test21_new_value
    )

[1] => stdClass Object
    (
        [id] => 54
        [value] => test54_new_value
    )
...

I want to update my first array $x importing value of the second array's ($y) field which has the same id, I want to have :

[0] => stdClass Object
    (
        [id] => 54
        [value] => test54_new_value
        [something] => testtest54
    )

[1] => stdClass Object
    (
        [id] => 21
        [value] => test21_new_value
        [something] => testtest21
    )
...

I can do something like this :

foreach($x as $k => $v) {
    foreach($y as $k2 => $v2) {
        if ($v->id === $v2->id) $x[$k]->value = $v2->value;
    }
}

But I don't like this, because I have to walk on array $y for each $x (if I have 100 items in $x and 100 items in $y, it loops 100*100 times). I think there is a more efficient, elegant or optimized way to do this, but I don't know how to do that (I did not found a precise response to this specific problem, so I ask here).

h2ooooooo · Accepted Answer · 2013-10-29 16:43:03Z

2

Sure. Usually you'd use an associative array for this (with the key being the unique ID), as this would mean (100 + 100) iterations instead of (100 * 100):

<?php
    $assocX = array();
    foreach ($x as $v) {
        $assocX[$v->id] = $v;
    }

    foreach ($y as $v) {
        $v->something = $assocX[$v->id]->something;
    }
?>

If you can't be sure that the value exists in $x you can also check for this ("no value" would be translated to NULL):

<?php
    $assocX = array();
    foreach ($x as $v) {
        $assocX[$v->id] = $v;
    }

    foreach ($y as $v) {
        $v->something = (isset($assocX[$v->id]) ? $assocX[$v->id]->something : null);
    }
?>

edited Oct 29, 2013 at 16:43

answered Oct 29, 2013 at 16:07

h2ooooooo

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2 Comments

rap-2-h Over a year ago

Ok thanks a lot ! Actually, the & isn't necessary with objects arrays, I think. $v already is a reference to an object (I've just tried with one loop, but maybe I'm wrong or I don't understood)

h2ooooooo Over a year ago

@rap-2-h You're right. Objects are always passed by reference (forgot that - it's late-ish!) :)

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