Adding one character to each array key in PHP

Question

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Fastest way to add prefix to array keys?

I had a quick question about arrays in PHP. I need to add a couple of characters to each key in an array, for instance:

name => Mark age => 23 weight = > 150

needs to be converted to:

r_name => Mark r_age => 23 r_weight => 150

Any help would be appreciated, thanks.

duplicate of a lot of posts, in fact – roirodriguez May 13 '11 at 13:04 — roirodriguez, May 13 '11 at 13:04

score 15 · Accepted Answer · answered May 13 '11 at 13:02

15

Iterate the array, add a new item with the modified key and delete the original item:

foreach ($arr as $key => $val) {
    $arr['r_'.$key] = $val;
    unset($arr[$key]);
}

As foreach works with an internal copy of the array, you won’t run into an infinite loop.

answered May 13 '11 at 13:02

Gumbo

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"As foreach works with an internal copy of the array, you won’t run into an infinite loop"... Good point! – roirodriguez May 13 '11 at 13:07
Whoa, didn't know of that internal copy thing. Up for that! – nocksock May 13 '11 at 13:11

score 1 · Answer 2 · edited May 23 '17 at 11:59

1

Take a look at this post: In PHP, how do you change the key of an array element?

edited May 23 '17 at 11:59

Community

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answered May 13 '11 at 13:03

roirodriguez

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score 1 · Answer 3 · answered May 13 '11 at 14:18

If you can be sure, that there are no two keys $K1,$K2 in your array with $K1 = "r_".$K2 , you can use the solution given by Gumbo - its efficient and nice.

If you can not guarantee the stated condition, i would prefer generating a new array with the altered keys and deleting/overwriting the old one afterwards. This is not as memory efficient as the other solution but wont fail.

Another thing to keep in mind is, that unset is a bit slow in PHP. So Unsetting a lot of elements in your array might be slower than working with a copy and deleting the original afterwards.

Adding one character to each array key in PHP

3 Answers3