Update value of key in array - php

Question

I want to multiply the value of all 'imdb' keys by 10 and update the value. In the code below when I print_r $horrorMovies it just shows I have created a new array with the required amounts. Its almost there if i do
$horrorMovies[0]['imdb'] = $imdbPercent;
But the values just get written to the first nested array.
Im not sure how to make this work with foreach, if it is possible.
function imdbMultiply($n) {
return($n['imdb'] * 10);
}
$horrorMovies = array(
array(
"title" => "The babadook",
"imdb" => 6.8,
"rotten" => 98
),
array(
"title" => "The shining",
"imdb" => 8.4,
"rotten" => 87
)
);
$imdbPercent = array_map("imdbMultiply", $horrorMovies);
$horrorMovies['imdb'] = $imdbPercent;

Answer 1

There's a few problems with your code:
Your imdbMultiply function needs to return the $n array, but modified so the imdb key is multiplied by 10.
array_map returns the new array, so you should set $horrorMovies to the result of array_map
In the end, your code should look like this:
function imdbMultiply ($n) {
$n['imdb'] *= 10;
return $n;
}
$horrorMovies = array_map('imdbMultiply', $horrorMovies);

Answer 2

//original data
$horrorMovies = array(
array(
"title" => "The babadook",
"imdb" => 6.8,
"rotten" => 98
),
array(
"title" => "The shining",
"imdb" => 8.4,
"rotten" => 87
)
);
//define "transformation" function, note that the argument is passed via reference
function imdbMultiply(&$n) {
$n['imdb'] *= 10;
}
//one option is to use foreach and then unset the reference to the
//last array element
foreach($horrorMovies as &$v){
$v['imdb'] *= 10;
}
unset($v);
print_r($horrorMovies);
//alternatively, one might apply the "transformation" function
//directly to each array element without the need to create a copy
array_walk($horrorMovies, "imdbMultiply");
print_r($horrorMovies);

Answer 3

You can just foreach the subarray[imdb] items.
$horrorMovies = array(
array(
"title" => "The babadook",
"imdb" => 6.8,
"rotten" => 98
),
array(
"title" => "The shining",
"imdb" => 8.4,
"rotten" => 87
)
);
foreach($horrorMovies as &$subarray){
$subarray["imdb"] *= 10;
}
var_dump($horrorMovies);
https://3v4l.org/ub40E

Answer 4

You just need to go into a loop and change the 'imdb' values, add the next
for loop to your code:
for ($i=0; $i<count($horrorMovies); $i++){
$horrorMovies[$i]['imdb']*=10;
}

Answer 5

If I understand what you expect, your imdbMultiply() function should be the following to be used with array_map :
function imdbMultiply($n) {
$n['imdb'] *= 10;
return $n;
}
Is it what you expect ?
Another idea is to use array_walk function, but you should define your imdbMultiply() function like this :
function imdbMultiply(&$n) {
$n['imdb'] *= 10;
}
The usage of array_walk is different :
array_walk($horrorMovies, "imdbMultiply");
var_dump($horrorMovies);