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Building dynamic cascading drop-down menus in Laravel Blade using JSON data
Building dynamic cascading drop-down menus in Laravel Blade using JSON data
Jul 23, 2025 pm 06:21 PM
1. Introduction
In web development, it is often necessary to load data from static data sources (such as JSON files) and display it interactively on front-end pages, such as building cascading selectors. The Laravel framework combines its powerful Blade template engine and front-end JavaScript capabilities to achieve this requirement gracefully. This article will use an address selector as an example to explain in detail how to use JSON data to build a dynamic cascading drop-down menu.
Suppose we have a JSON file with region, town, quarter, and postal codes:
[
{
"Region": "Naypyitaw Union Territory",
"Town ": "Za Bu Thi Ri Township",
"Quarter": "Zay Ya Theik Di Quarter",
"Postal Code": 1501001
},
{
"Region": "Naypyitaw Union Territory",
"Town ": "Za Bu Thi Ri Township",
"Quarter": "Pyin Nyar Theik Di Quarter",
"Postal Code": 1501002
},
{
"Region": "Another Region",
"Town ": "Some Town",
"Quarter": "Some Quarter",
"Postal Code": 2000001
}
]
Our goal is: When the user selects a "Region", the "Town" drop-down menu will automatically update all towns under the area; when the "Town" is selected, the "Quarter" drop-down menu will automatically update all quarters under the town.
2. Data preparation: JSON processing in the controller
First, we need to read the JSON file in the Laravel controller and parse it into a PHP array and pass it to the Blade view.
<?php namespace App\Http\Controllers;
use Illuminate\Http\Request;
class UserController extends Controller
{
/**
* Display create user form and load address data.
*
* @return \Illuminate\View\View
*/
public function create()
{
// Make sure the JSON file is located in resources/data/address.json
$jsonFilePath = base_path('resources/data/address.json');
// Check if the file exists if (!file_exists($jsonFilePath)) {
// Handle the case where the file does not exist according to actual needs, such as throwing an exception or returning an error message abort(500, 'Address data file not found.');
}
$jsonString = file_get_contents($jsonFilePath);
// Decode the JSON string into a PHP array// The second parameter 'true' means decoded as an associative array, not the object $details = json_decode($jsonString, true);
// Check whether JSON decoding is successful if (json_last_error() !== JSON_ERROR_NONE) {
// Handle JSON parsing error abort(500, 'Failed to decode address data: ' . json_last_error_msg());
}
// Pass data to the view return view('users.create')->with('details', $details);
}
}
Code explanation:
- base_path('resources/data/address.json'): Get the absolute path to the JSON file. It is recommended to place static data files in the resources directory for easy management.
- file_get_contents(): Read the contents of the entire file to a string.
- json_decode($jsonString, true): Decode the JSON string into a PHP data structure. The key is the second parameter true, which forces the JSON object to be decoded into a PHP associative array, which is more convenient when accessing data through key names in the Blade template (e.g. $detail['Region']). If there is no true, it will be decoded as a PHP object and needs to be accessed through $detail->Region.
- json_last_error() and json_last_error_msg(): used to check whether an error occurs during the JSON decoding process, which is very important in production environments.
3. Basic display: traverse and display data in Blade
After the controller passes the $details data to the users.create view, we can traverse this data in the Blade template to build the first drop-down menu (e.g. "Region").
<!-- resources/views/users/create.blade.php -->
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Create user</title>
<h1>Create a new user</h1>
The above is the detailed content of Building dynamic cascading drop-down menus in Laravel Blade using JSON data. For more information, please follow other related articles on the PHP Chinese website!
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