In PHP, how do you change the key of an array element?


Question

I have an associative array in the form key => value where key is a numerical value, however it is not a sequential numerical value. The key is actually an ID number and the value is a count. This is fine for most instances, however I want a function that gets the human-readable name of the array and uses that for the key, without changing the value.

I didn't see a function that does this, but I'm assuming I need to provide the old key and new key (both of which I have) and transform the array. Is there an efficient way of doing this?

1
323
10/27/2008 5:09:48 PM

Accepted Answer

$arr[$newkey] = $arr[$oldkey];
unset($arr[$oldkey]);
516
10/27/2008 5:12:45 PM

The way you would do this and preserve the ordering of the array is by putting the array keys into a separate array, find and replace the key in that array and then combine it back with the values.

Here is a function that does just that:

function change_key( $array, $old_key, $new_key ) {

    if( ! array_key_exists( $old_key, $array ) )
        return $array;

    $keys = array_keys( $array );
    $keys[ array_search( $old_key, $keys ) ] = $new_key;

    return array_combine( $keys, $array );
}

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