PHP return reference from recursive function

Question

I'm trying to make a recursive function which searches a specific element by value (blubb) in a multidimensional array and returns it as a reference. But my first thought does not work. I'm sure I just missed something simple.

$array = [
    'obj1' => [
        'attr1' => "blubb",
        'attr2' => "bla"
        ],
    'obj2' => [
        'attr1' => "blabb",
        'attr2' => "bla"
        ]
    ];

$node = changeAttr2($array);
$node["attr2"] = "blu";

print_r($node);
print_r($array);

function changeAttr2(&$input) {
    foreach($input as &$value) {
        if ($value === "blubb") {
            return $input;
        }

        return changeAttr2($value);
    }
}

Output:

Array
(
    [obj1] => Array
        (
            [attr1] => blubb
            [attr2] => bla
        )

    [obj2] => Array
        (
            [attr1] => blabb
            [attr2] => bla
        )

)

Expected Output:

Array
(
    [obj1] => Array
        (
            [attr1] => blubb
            [attr2] => blu
        )

    [obj2] => Array
        (
            [attr1] => blabb
            [attr2] => bla
        )

)

Your function does not return a reference. Read the documentation page about how to return references. — axiac
– axiac, Commented Jan 11, 2018 at 9:22

apokryfos · Accepted Answer · 2018-01-11 09:15:59Z

1

You pass the array by reference but when you return it you're not actually returning a reference.

Do this (honestly this looks very dirty and needs rethinking but this is how you do it if you really really need to):

<?php
$array = [
    'obj1' => [
        'attr1' => "blubb",
        'attr2' => "bla"
        ],
    'obj2' => [
        'attr1' => "blabb",
        'attr2' => "bla"
        ]
    ];

$node = &changeAttr2($array);
$node["attr2"] = "blu";

print_r($node);
print_r($array);

function &changeAttr2(&$input) {
    foreach($input as &$value) {
        if ($value === "blubb") {
            return $input;
        }

        return changeAttr2($value);
    }
}

Prints:

Array
(
    [obj1] => Array
        (
            [attr1] => blubb
            [attr2] => blu
        )

    [obj2] => Array
        (
            [attr1] => blabb
            [attr2] => bla
        )

)

Reason is you need to return the reference and use it as a reference.

more detail in the manual on returning references

answered Jan 11, 2018 at 9:15

apokryfos

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1 Comment

Philipp Spinnler Over a year ago

Thank you alot. I know it is super dirty an I'm going to rethink it. But for now this helps to create a prototype.

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