PHP & HTML : how to create dynamic drop down list - php

Question

I have a little problem.
I'm searching the internet now for quite some time to find a proper solution but I was not successful so far.
This is what I want :
First, I choose Category
Then, in second selection contain all the store result from category selection.
this is my first drop down list which is contain Category :
<select name="category" class="form-control" id="select1">
<option value="-1"> - Choose One -</option>
<?php
$StoreCategoriesAPIAccessor = new StoreCategoriesAPIService(GuzzleClient::getClient());
$stores = $StoreCategoriesAPIAccessor->getStoreCategories();
foreach ($stores as $store):
?>
<option value="<?php echo $store->getStoreCategoryId(); ?>"><?php echo $store->getCategory(); ?></option>
<?php endforeach; ?>
</select>
this is my second drop down list :
<select name="category" class="form-control" id="select2">
<option value="-1"> - Choose One -</option>
<?php
$StoreAPIAccessor = new StoreAPIService(GuzzleClient::getClient());
$stores = $StoreAPIAccessor->getStores();
foreach ($stores as $store):
?>
<option value="<?php echo $store->getStoreId(); ?>"><?php echo $store->getStoreName(); ?></option>
<?php endforeach; ?>
</select>
Anyone know how to implement dynamic drop down list for this case ?

Answer 1

Well first of all I'd like to ask that you separate business logic from view logic as much as possible, so I will do that in this answer.
Secondly, the 2nd dropdown box logic that you have does not contain anything that would retrieve stores for a given category, I will therefore make some assumptions and you can adjust based on that.
<?php
$StoreCategoriesAPIAccessor = new StoreCategoriesAPIService(GuzzleClient::getClient());
$categories = $StoreCategoriesAPIAccessor->getStoreCategories();
if (!empty($_GET['category'])) {
$category_id = $_GET['category'];
$StoreAPIAccessor = new StoreAPIService(GuzzleClient::getClient());
$stores = $StoreAPIAccessor->getStores($category_id); // Assumption, the call to getStores() accepts category_id as a parameter
} else { // Optional as you don't need to declare variables in PHP, but its better practice to do so
$category_id = null;
$stores = array();
}
?>
<select id="select_category" name="category" class="form-control" onchange="window.location='?category=' + this.value">
<option value="">- Choose One -</option>
<?php foreach ($categories as $category): ?>
<option value="<?php echo $category->getStoreCategoryId() ?>"><?php echo $category->getCategory() ?></option>
<?php endforeach ?>
</select>
<select id="select_store" name="store" class="form-control"<?php echo $category_id == null ? " disabled='disabled'" : "">
<option value="">- Choose One -</option>
<?php foreach ($stores as $store): ?>
<option value="<?php echo $store->getStoreId() ?>"><?php echo $store->getStoreName() ?></option>
<?php endforeach ?>
</select>