Looking for function similar to array_map but which the same arg each time to the callback

Question

As someone who is learning PHP I was experimenting with the arrap_map function. I was hoping that it would pass the same 3rd arg each time through to the called function. As below, this is not the behaviour of array_map. Is there an alternative function I can use to achieve this?

$arr = [['a'], ['b'], ['c']];
$args = ['set'];

function mapper($item, $arg){
return $item[] = $arg;
}
$result = array_map('mapper', $arr, $args);

only the first element has 'set' as a value

 $arr = [['a'], ['b'], ['c']];
$args = ['set', 'set', 'set'];

function mapper($item, $arg){
return $item[]  = $arg;
}

$result = array_map('mapper', $arr, $args);

all three elements have 'set' as a value

I think `array_fill_keys()` is better for what you want to do. — Rizier123, Dec 03 '15 at 11:39
"pass the 3rd argument through each time?" - and what exactly should it pass? — Karoly Horvath, Dec 03 '15 at 12:36

score 1 · Accepted Answer · answered Dec 03 '15 at 12:29

1

Your code is incorrect, $a[$b] doesn't make any sense. Both variables are strings.

Your output also doesn't make sense, quoting from the manual:

If more than one argument is passed then the returned array always has integer keys.

To answer your question, it's a language design choice.

It could

pass NULL for missing elements (that was PHP does).
throw an error if the inputs don't have the same size.
cycle the smaller inputs.

All these have valid applications and their own problems.

answered Dec 03 '15 at 12:29

Karoly Horvath

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@AndrewWelch Now after you updated your question it simply comes down to a misunderstanding how `array_map()` works. With `array_map()` you go through each element of every array which you passed to it. – Rizier123 Dec 03 '15 at 12:51
`echo "$a $b";` :) or `var_dump` if you want to see the `NULL`. – Karoly Horvath Dec 03 '15 at 12:53
Ok, so now you removed the text about what it "returns", but it's the *same* nonsensical code. I'm out. – Karoly Horvath Dec 03 '15 at 12:56
@KarolyHorvath - can you delete your answer, so I can delete the questions please. – weaveoftheride Dec 03 '15 at 19:39

Looking for function similar to array_map but which the same arg each time to the callback

1 Answers1