Swap array keys where found in php

Question

I start with a MySQL query (not of my design) that returns results that look like:

 $row['user_name'];
 $row['user_property']
 $row['user_property_2']
 $row['day_1']
 $row['day_2']
 $row['day_3']
 $row['day_4']
 $row['day_5']

What I would like to do is quickly (ideally in one step, not in a loop) replace (re-key) all of the field names that contain 'day_' to just have the number, resulting in:

 $row['user_name'];
 $row['user_property']
 $row['user_property_2']
 $row['1']
 $row['2']
 $row['3']
 $row['4']
 $row['5']

but without any risk to the other field name keys.

I imagine some solution that involves an "swap" array like:

 $swap_array = ('day_1' => 1, 'day_2' => 2,'day_3' => 3, 'day_4' => 4, 'day_5' => 5);

But I'm not sure what function to implement the swap array. I am sure I've seen a native function for this before, but can't find it.

score 2 · Accepted Answer · answered Jan 31 '11 at 05:35

$arr = 
array_combine(
  explode(',', 
    preg_replace('/day_/', '', implode(',', array_keys($row)))), $row);

PS: what's wrong with loop?

potential problem 1 - if the return key like day_now might cause problem
potential problem 2 - if the return key contains comma, might cause problem

however, both potential problems can be fixed by enhance the regexp above

as for the native function, is array_map that you looking for?

score 1 · Answer 2 · answered Jan 31 '11 at 05:37

1

The only way I can think of it without looping is by using array_map:

$result = array_map(function($value, $key) use($swap_array) {
  return array(
    $value,
    isset($swap_array[$key]) ? $swap_array[$key] : $key
  );
}, $input_array);

answered Jan 31 '11 at 05:37

mhitza

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score 1 · Answer 3 · answered Jan 31 '11 at 05:49

The canonical method would be:

$key_map = array_replace(   # key => key               # XOR keys
    array_combine(array_keys($row), array_keys($row)), $swap_array
);
$row = array_combine(array_values($key_map), array_values($row));

However I would think that string replacement or any manual mapping would be faster and more readable.

Swap array keys where found in php

3 Answers3