How can I rename some keys in a PHP array using another associative array?

Question

Given a data array ...

$data_array = array (
"old_name_of_item" => "Item One!"
);

... and a rename array ...

$rename_array = array (
"old_name_of_item" => "new_name_of_item"
);

... I would like to produce an output like this:

Array
(
    [new_name_of_item] => Item One!
)

I have written the following function, and while it works fine, I feel like I'm missing some features of PHP.

function rename_keys($array, $rename_array) {
foreach( $array as $original_key => $value) {
    foreach( $rename_array as $key => $replace ) {
        if ($original_key == $key) {
            $array[$replace] = $value;
            unset($array[$original_key]); 
        }
    }
}
return $array;
}

Does PHP offer built-in functions to help with this common problem? Thanks!

@Sammitch: I've seen it twice today: php key name change issue in associative array — AbraCadaver
– AbraCadaver, Commented Mar 3, 2014 at 19:47

Philippe Signoret · Accepted Answer · 2014-03-03 20:15:16Z

1

You only have to go through the array once:

function rename_keys($array, $rename_array) {
    foreach ( $rename_array as $original_key => $value ) {
        if (isset($array[$original_key])) {
            $array[$rename_array[$original_key]] = $array[$original_key];
            unset($array[$original_key]);
        }
    }
}

This assumes, of course, that both arrays are correctly filled (unique values for the replacement keys).

Edit: only replace if a corresponding element exists in $rename_array.

Edit 2: only goes through $rename_array

edited Mar 3, 2014 at 20:15

answered Mar 3, 2014 at 19:42

Philippe Signoret

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7 Comments

James Over a year ago

You don't need to go through every value in $array, just every value in $rename_array which should be quicker

Martin Burch Over a year ago

What do you mean by "correctly"? All keys in the same order, same keys in both arrays?

Martin Burch Over a year ago

@James could you post an answer that shows how that would work?

Philippe Signoret Over a year ago

@James, you're right! Martin, replacement keys should be unique. Updated answer to reflect both of these.

Martin Burch Over a year ago

Oh, I see, so if there was a duplicate key, it wouldn't get renamed. I think we can deal with that. There shouldn't be duplicate keys. The major improvement in your answer is that, compared to my code, isset() replaces foreach() loop.

|

AbraCadaver · Accepted Answer · 2014-03-03 19:44:29Z

0

Second time today. This one is easier:

$data_array = array_combine(
        str_replace(array_keys($rename_array), $rename_array, array_keys($data_array)), $data_array);

answered Mar 3, 2014 at 19:44

AbraCadaver

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1 Comment

Philippe Signoret Over a year ago

To answer my own question: this answer is much slower than the my answer. In the worst case (replace all keys), this took 10x longer for 100 elements, 1000X slower for 1000 elements, etc...

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