PHP - Access an array using another array as the key - php

Question

I'm creating a class that assists in building settings pages for WordPress plugins. The developer instantiates the class by passing in an array of settings. A basic example looks like:
Array
(
[textbox1] => Array
(
[title] => Textbox
[type] => text
[section] => general
[desc] => The text description
)
[a_nice_dropdown] => Array
(
[title] => Select me
[type] => select
[section] => general
[desc] => The select description
[choices] => Array
(
[red] => Red
[blue] => Blue
[green] => Green
)
)
)
This works fine. My class builds the options page and the inputs have HTML that looks like:
<input id="textbox1" type="text" name="options_slug[textbox1]" value="">
When "Save Changes" is clicked, my class grabs all the options tied to "options_slug" and stores them in a single wp_options entry as a nice serialized array, making it easy to grab later.
The New Challenge
I have a new project which requires multiple nested "repeater" fields, similar to the way Advanced Custom Fields handles it. I've created a new field type, to handle this, which can support "subfields". An example config output (from error_log) looks like:
Array
(
[subfields_container] => Array
(
[title] => Subfields
[type] => subfields
[section] => general
[desc] => This is the subfields description text
[subfields] => Array
(
[textbox2] => Array
(
[title] => Textbox
[type] => text
[section] => general
[desc] => The text description
)
[select1deep] => Array
(
[title] => Subfield Select
[type] => select
[choices] => Array
(
[1] => 1
[2] => 2
[3] => 3
)
[std] => 1
)
)
)
)
I've configured the HTML output so an input inside a "subfields" container now looks like:
<input id="textbox1" type="text" name="options_slug[subfields_container][textbox2]" value="">
The idea being that the end user can easily group fields: i.e.,
$options = get_option('options_slug');
foreach($options['subfield_container'] as $subfield) {
// etc...
}
The Problem
As I iterate through these multidimensional arrays, I need to continually update a $options variable at the current index so it can be saved to the DB. So where previously I was able to do:
$id = 'textbox1';
$options[$id] = $_POST['textbox1'];
Now I'm doing something like:
$id = array('subfields_container' => 'textbox2');
$options[$id] = $_POST['textbox2'];
But I get "illegal offset type" errors. Because I can't set an array property using another array.
I've considered just putting dashes in the ID's instead of creating a hierarchical array, something like:
<input id="textbox1" type="text" name="options_slug[subfields_container-textbox2]" value="">
But then I'll lose the ability to foreach over a specific part of the stored options.
The Question
What's the best way to dynamically set a value inside of a multidimensional array when the array is not fixed in structure?
Thank you

Answer 1

I'd suggest to just dynamically create a multi-leveled array:
$arr = array();
$arr['subfields_container']['textbox1'] = $_POST['textbox1'];
print_r($arr);
=>
Array
(
[subfields_container] => Array
(
[textbox1] => <POSTed value>
)
)
All of the non-existent keys will just be created on the fly, regardless of the number of nested levels you specify.
Update
Given that the user can arbitrarily specify any number of nesting levels as elucidated below, you probably want a recursive function that returns the values for all the elements of the current level, and calls itself to retrieve the values for any elements at the current level that contain sub elements.
Example:
function getNestedPostVars($config, $formName, $keys = array()) {
$output = [];
foreach ($config as $label => $fieldConfig) {
if (isset($config['subfields'])) {
$output[$label] = getNestedPostVars(
$config['subfields'],
$formName,
array_merge($keys, array($label))
);
continue;
}
$output[$label] = /* path to $_POST element using $keys/$label */ ;
}
return $output;
}