Overwrite the original array values in PHP in nested loop - php

Question

Cutting out some of the code on the innermost foreach, I'm trying to change HERE to make it so that it alters the original value. I want to pass a pointer basically and alter it. I was able to kind of do this with the &$ keyword in the foreach but (as the docs state) it results in some buggy behavior and I'm trying to do it the way they, and others on SO suggest. The problem is all the examples I find are for a single foreach, not for nested.
The following code loops properly but when I get to the HERE it doesn't actually alter the original value. Also worth mentioning that $sources could be an array of arrays (by index) or an array of key values. This looping code seems to iterate over both fine though, just not overriding the original value of $sources
fwiw, on top of the &$ I also tried:
$sources[$sourceKey][$rowKey][$cellKey] = $date->format('m/d/Y');
Which $sources[$sourceKey][$rowKey][$cellKey] returns the right value if I print it but it still doesn't overwrite the original array.
function convertDates($sources) {
foreach($sources as $sourceKey => $sourceValue){
foreach ($sourceValue as $rowKey => $rowValue) {
foreach ($rowValue as $cellKey => $cellValue) {
HERE = $date->format('m/d/Y');
}
}
}
}

Answer 1

I never could get this to work correctly since there were two formats this loop could get (JSON encoded object and an array). Making it work for both was much harder than just doing it in JavaScript so instead of modifying on the server I format the data how I want client side and send it up. This formatting is purely presentational and for personal use so if someone were to put in a debugger and change the code to send a different format thats fine and there's no security issues.
So in the end, this code was rewritten in JS and since JS handles arrays and objects using the same pointers the above issue wasn't an issue any longer.