PHP change value of array by reference

Question

Here's sample code:

<?php

$arr1 = [ 'foo' => 'bar', 'test' => '2' ];
$arr2 = [ 'foo' => 'bar', 'test' => '2' ];

$arr3 = [ $arr1, $arr2 ];

$randomArr = $arr3[mt_rand(0, count($arr3) -1)];

$randomArr['test'] = 3;

echo "$arr1: " . print_r($arr1, true);
echo "$arr2: " . print_r($arr2, true);

What I'm trying to do here is change the value of $arr1['test'] or $arr2['test'], at random, to 3. It seems $randomArr gets copied by value and not by reference. Is there a way to do a copy by reference so that I can change $arr1 or $arr2 inline?

php.net/manual/en/language.references.php

aynber
– aynber

2017-09-07 19:46:04 +00:00
Commented Sep 7, 2017 at 19:46 — aynber
– aynber, Commented Sep 7, 2017 at 19:46

Don't Panic · Accepted Answer · 2017-09-07 19:48:55Z

6

You can create an array of references to your other arrays.

$arr3 = [ &$arr1, &$arr2 ];

Then update one of the arrays directly without creating $randomArr.

$arr3[mt_rand(0, count($arr3) -1)]['test'] = 3;

answered Sep 7, 2017 at 19:48

Don't Panic

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2 Comments

randombits Over a year ago

What if multiple keys need to have their values updated for the same array?

Don't Panic Over a year ago

In that case you could create $randomArr as before, but assign it by reference as well. Pretty much like the other answer that @gview added just as I replied to your comment :)

gview · Accepted Answer · 2017-09-07 19:52:46Z

4

Or you can using your code do this as well:

<?php

$arr1 = [ 'foo' => 'bar', 'test' => '2' ];
$arr2 = [ 'foo' => 'bar', 'test' => '2' ];

$arr3 = [ &$arr1, &$arr2 ];

$randomArr = &$arr3[mt_rand(0, count($arr3) -1)];

print_r($randomArr);
$randomArr['test'] = 3;

echo "$arr1: " . print_r($arr1, true);
echo "$arr2: " . print_r($arr2, true);

answered Sep 7, 2017 at 19:52

gview

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