Cannot modify multidimensional array PHP - php

Question

I have two arrays.
First one ($dcel) looks like this:
Array(
[1] => Array
(
[V1] => 5
[V2] => 2
[F1] => 4
[F2] => 1
[P1] => 7
[P2] => 4
)
etc..
Second one ($PctOldNew) looks like this:
Array(
[0] => Array
(
[old] => 1
[new] => 3
)
etc..
I'm trying to find the 'old' values (which are the initial) in the first array. Here's my code:
foreach ($dcel as $latura) {
for($i = 0; $i <= $nrPct; $i++){
if($PctOldNew[$i]['old'] == $latura[V1]){
$latura[V1] = $PctOldNew[$i]['new'];
}
}
}
If I output the $PctOldNew inside if statment, the output it's the correct answer, but if i try to modify $latura[V1] the $dcel remains untouched.
I've tried with reference, keys... but nothing works and i can't see what's wrong.

Answer 1

This works:
edit: adding a 2nd array element to $dcel to show how it works
<?php
$dcel = Array(
'1' => Array
(
'V1' => 1, // <-- note that i changed this value from your original '5' to '1' so that your condition will actually match something, since this example data set doesn't actually have something to match
'V2' => 2,
'F1' => 4,
'F2' => 1,
'P1' => 7,
'P2' => 4
)
'2' => Array
(
'V1' => 5,
'V2' => 2,
'F1' => 4,
'F2' => 1,
'P1' => 7,
'P2' => 4
)
);
$PctOldNew = Array(
'0' => Array
(
'old' => 1,
'new' => 3
)
);
foreach ($dcel as &$latura) { // <-- reference on &$latura
for($i = 0; $i <= $nrPct; $i++){
if($PctOldNew[$i]['old'] == $latura['V1']){
$latura['V1'] = $PctOldNew[$i]['new'];
}
}
}
echo "<pre>";print_r($dcel);
output
Array
(
[1] => Array
(
[V1] => 3
[V2] => 2
[F1] => 4
[F2] => 1
[P1] => 7
[P2] => 4
)
[2] => Array
(
[V1] => 5
[V2] => 2
[F1] => 4
[F2] => 1
[P1] => 7
[P2] => 4
)
)

Answer 2

#CrayonViolent it didn't work, i tried so many times.
I was playing right now with the code and it seems that like this it's working:
foreach ($dcel as $key => $value) {
foreach ($value as $val) {
for($i = 0; $i <= $nrPct; $i++){
if($PctOldNew[$i]['old'] == $value[V1])
$new = $PctOldNew[$i]['new'];
}
$val = $new;
}
$dcel[$key][V1] = $val;
}
...but i don't know why.

Answer 3

The most convenient way in your case would be using array_map() function
Like this:
$array = array(1,2,3,4,5);
$replacements = array(
array('old'=>1, 'new'=>11),
array('old'=>3, 'new'=>33),
);
$array = array_map(function($element){
global $replacements;
foreach($replacements as $r) if($r['old']==$element) return $r['new'];
return $element;
}, $array);
print_r($array);
Result:
Array ( 11, 2, 33, 4, 5 )

Answer 4

Another weird way is to use array_walk
array_walk(&$dcel, function($latura){
for($i = 0; $i <= $nrPct; $i++){
if($PctOldNew[$i]['old'] == $latura[V1]){
$latura[V1] = $PctOldNew[$i]['new'];
}
}
});
Or array_map
$dcel = array_map(function($latura){
for($i = 0; $i <= $nrPct; $i++){
if($PctOldNew[$i]['old'] == $latura[V1]){
$latura[V1] = $PctOldNew[$i]['new'];
}
}
return $latura;
}, $dcel);
(Not sure why array_walk and array_map have reversed parameter position)
Updated with the real reason and 2 more possible solutions
The reason you can't modify $latura is because you are using for...each loop which will pass $latura by-value rather than by-reference. Based on this reason, you have 2 more solutions,
Use for $dcel as $key => $latura then you can change $dcel[$key]
Use for $dcel as &$latura then you can change the item directly