Access Multi dimensional array through a dynamic variable - php

Question

I am trying to pass a dynamic variable into a multidimensional array.
This is the actual code:
for($i = 0; $i < count($social ["#object"] -> field_sector ["und"]); $i++){
echo $social ["#object"] -> field_sector ["und"] [$i] ["taxonomy_term"] -> name;
}
Since I want to re-use this code for multiple types, I created a function
function render_multi_array ($parent, $field_name) {
for($i = 0; $i < count($parent ["#object"] -> $field_name ["und"]); $i++){
echo $parent ["#object"] -> $field_name ["und"] [$i] ["taxonomy_term"] -> name;
}
}
The issue is happening with $field_name as I am unable to provide this dynamically. Any idea how I can make this function work?
Sample array is follows:
Array
(
[#title] => Sector
[#field_name] => field_sector
[#object] => stdClass Object
(
[vid] => 1079
[uid] => 30
[vuuid] => 83ab0817-0175-4541-b20e-93611c20c026
[nid] => 1077
[type] => random_study
[field_random_id] => Array
(
[und] => Array
(
[0] => Array
(
[value] => CS_525
[format] =>
[safe_value] => CS_525
)
)
)
[field_sector] => Array
(
[und] => Array
(
[0] => Array
(
[tid] => 411
[taxonomy_term] => stdClass Object
(
[tid] => 411
[vid] => 10
[name] => Sample title goes here.
)
)
[1] => Array
(
[tid] => 248
[taxonomy_term] => stdClass Object
(
[tid] => 248
[vid] => 10
[name] => Energy
)
)
)
)

Answer 1

In PHP 7 the code should work as written. PHP 7.0 changed evaluation order to strictly left to right.
In PHP 5, you'll get an illegal string offset warning because PHP is trying to first evaluate $field_name["und"] (e.g. "field_sector"["und"]) and use the result of that as the property name in #object rather than evaluating $parent["#object"]->$field_name to get the array and then accessing that with ["und"].
You can prevent that by bracketing the variable like this:
function render_multi_array ($parent, $field_name) {
for ($i = 0; $i < count($parent["#object"]->{$field_name}["und"]); $i++){
echo $parent ["#object"]->{$field_name}["und"][$i]["taxonomy_term"]->name;
}
}
Adding those brackets won't cause any problems if you upgrade to PHP 7 later.
By the way, it looks like this code would be simpler with a foreach loop instead.
function render_multi_array ($parent, $field_name) {
foreach ($parent['#object']->{$field_name}['und'] as $item) {
echo $item['taxonomy_term']->name;
}
}