code-boxx/0-PHP-AJAX-DEPENDENT-DROPDOWN.MD

## 0-PHP-AJAX-DEPENDENT-DROPDOWN.MD

      
    Raw
  

              0-PHP-AJAX-DEPENDENT-DROPDOWN.MD
            
          
    PHP AJAX DEPENDENT DROPDOWN

https://code-boxx.com/dependent-dropdown-ajax-php-mysql/
NOTES


Create a test database and import 1-db.sql.
Change the database settings in 2-lib.php to your own.
Launch 4-selector.html in the browser. Captain Obvious – Use http:// not file://.

LICENSE

Copyright by Code Boxx
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

  
## 1-db.sql
-- (A) CATEGORY TABLE
CREATE TABLE `category` (
  `id` bigint(20) NOT NULL,
  `parent` bigint(20) NOT NULL DEFAULT 0,
  `name` varchar(255) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

ALTER TABLE `category`
  ADD PRIMARY KEY (`id`),
  ADD KEY `parent` (`parent`),
  ADD KEY `name` (`name`);

ALTER TABLE `category`
  MODIFY `id` bigint(20) NOT NULL AUTO_INCREMENT, AUTO_INCREMENT=10;

-- (B) DUMMY DATA
INSERT INTO `category` (`id`, `parent`, `name`) VALUES
(1, 0, 'Electronics'),
(2, 0, 'Sports'),
(3, 1, 'Mobile'),
(4, 1, 'Tablet'),
(5, 1, 'Laptop'),
(6, 1, 'Desktop'),
(7, 2, 'Jogging'),
(8, 2, 'Swimming'),
(9, 2, 'Cycling');

## 2-lib.php
<?php
class Category {
  // (A) CONSTRUCTOR - CONNECT TO DATABASE
  private $pdo = null;
  private $stmt = null;
  public $error = null;
  function __construct () {
    $this->pdo = new PDO(
      "mysql:host=".DB_HOST.";dbname=".DB_NAME.";charset=".DB_CHARSET,
      DB_USER, DB_PASSWORD, [
      PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
      PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC
    ]);
  }

  // (B) DESTRUCTOR - CLOSE DATABASE CONNECTION
  function __destruct () {
    if ($this->stmt !== null) { $this->stmt = null; }
    if ($this->pdo !== null) { $this->pdo = null; }
  }

  // (C) GET BY PARENT CATEGORY
  function get ($pid) {
    $this->stmt = $this->pdo->prepare("SELECT * FROM `category` WHERE `parent`=?");
    $this->stmt->execute([$pid]);
    $results = [];
    while ($row = $this->stmt->fetch()) { $results[$row["id"]] = $row["name"]; }
    return $results;
  }
}

// (D) DATABASE SETTINGS - CHANGE TO YOUR OWN!
define("DB_HOST", "localhost");
define("DB_NAME", "test");
define("DB_CHARSET", "utf8mb4");
define("DB_USER", "root");
define("DB_PASSWORD", "");

// (E) NEW CATEGORY OBJECT
$_CAT = new Category();

## 3-ajax.php
<?php
// (A) LOAD LIBRARY
require "2-lib.php";

// (B) GET CATEGORIES
$id = isset($_POST["id"]) ? $_POST["id"] : 0 ;
echo json_encode($_CAT->get($id));

## 4a-selector.html
<!DOCTYPE html>
<html>
  <head>
    <title>Dependent Dropdown Selector</title>
    <meta charset="utf-8">
    <script src="4b-selector.js"></script>
    <link rel="stylesheet" href="4c-selector.css">
  </head>
  <body>
    <form onsubmit="return false;">
      <label>Main Category</label>
      <select id="cat1" onchange="loadcat(2)"></select>

      <label>Sub Category</label>
      <select id="cat2"></select>
    </form>
  </body>
</html>

## 4b-selector.js
// (A) LOAD CATEGORY SELECTOR
// level 1 = main category
// level 2 = sub category
function loadcat (level) {
  // (A1) GET SELECTED PARENT ID
  var data = new FormData();
  data.append("id", (level==1 ? 0 : document.getElementById("cat1").value));

  // (A2) AJAX FETCH CATEGORIES
  fetch("3-ajax.php", { method: "POST", body: data })
  .then(res => res.json())
  .then(cat => {
    // (A2-1) UPDATE HTML SELECTOR
    let selector = document.getElementById("cat" + level);
    selector.innerHTML = "";
    for (let i in cat) {
      let opt = document.createElement("option");
      opt.value = i;
      opt.innerHTML = cat[i];
      selector.appendChild(opt);
    }

    // (A2-2) CASCADE LOAD SUB-CATEGORY
    if (level==1) { loadcat(2); }
  });
}

// (B) INIT LOAD
window.onload = () => loadcat(1);

## 4c-selector.css
/* (X) DOES NOT MATTER */
* {
  font-family: Arial, Helvetica, sans-serif;
  box-sizing: border-box;
}
form {
  max-width: 400px;
  padding: 30px 20px;
  border: 1px solid #e1e1e1;
  background: #f2f2f2;
}
label, select {
  display: block;
  width: 100%;
}
label {
  margin: 10px 0;
  color: #4a4a4a;
}
form label:first-child { margin-top: 0; }
select {
  padding: 10px;
  border: 1px solid #d5d5d5;
}
	-- (A) CATEGORY TABLE
	CREATE TABLE `category` (
	`id` bigint(20) NOT NULL,
	`parent` bigint(20) NOT NULL DEFAULT 0,
	`name` varchar(255) NOT NULL
	) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

	ALTER TABLE `category`
	ADD PRIMARY KEY (`id`),
	ADD KEY `parent` (`parent`),
	ADD KEY `name` (`name`);

	ALTER TABLE `category`
	MODIFY `id` bigint(20) NOT NULL AUTO_INCREMENT, AUTO_INCREMENT=10;

	-- (B) DUMMY DATA
	INSERT INTO `category` (`id`, `parent`, `name`) VALUES
	(1, 0, 'Electronics'),
	(2, 0, 'Sports'),
	(3, 1, 'Mobile'),
	(4, 1, 'Tablet'),
	(5, 1, 'Laptop'),
	(6, 1, 'Desktop'),
	(7, 2, 'Jogging'),
	(8, 2, 'Swimming'),
	(9, 2, 'Cycling');
	<?php
	class Category {
	// (A) CONSTRUCTOR - CONNECT TO DATABASE
	private $pdo = null;
	private $stmt = null;
	public $error = null;
	function __construct () {
	$this->pdo = new PDO(
	"mysql:host=".DB_HOST.";dbname=".DB_NAME.";charset=".DB_CHARSET,
	DB_USER, DB_PASSWORD, [
	PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
	PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC
	]);
	}

	// (B) DESTRUCTOR - CLOSE DATABASE CONNECTION
	function __destruct () {
	if ($this->stmt !== null) { $this->stmt = null; }
	if ($this->pdo !== null) { $this->pdo = null; }
	}

	// (C) GET BY PARENT CATEGORY
	function get ($pid) {
	$this->stmt = $this->pdo->prepare("SELECT * FROM `category` WHERE `parent`=?");
	$this->stmt->execute([$pid]);
	$results = [];
	while ($row = $this->stmt->fetch()) { $results[$row["id"]] = $row["name"]; }
	return $results;
	}
	}

	// (D) DATABASE SETTINGS - CHANGE TO YOUR OWN!
	define("DB_HOST", "localhost");
	define("DB_NAME", "test");
	define("DB_CHARSET", "utf8mb4");
	define("DB_USER", "root");
	define("DB_PASSWORD", "");

	// (E) NEW CATEGORY OBJECT
	$_CAT = new Category();
	<?php
	// (A) LOAD LIBRARY
	require "2-lib.php";

	// (B) GET CATEGORIES
	$id = isset($_POST["id"]) ? $_POST["id"] : 0 ;
	echo json_encode($_CAT->get($id));
	<!DOCTYPE html>
	<html>
	<head>
	<title>Dependent Dropdown Selector</title>
	<meta charset="utf-8">
	<script src="4b-selector.js"></script>
	<link rel="stylesheet" href="4c-selector.css">
	</head>
	<body>
	<form onsubmit="return false;">
	<label>Main Category</label>
	<select id="cat1" onchange="loadcat(2)"></select>

	<label>Sub Category</label>
	<select id="cat2"></select>
	</form>
	</body>
	</html>
	// (A) LOAD CATEGORY SELECTOR
	// level 1 = main category
	// level 2 = sub category
	function loadcat (level) {
	// (A1) GET SELECTED PARENT ID
	var data = new FormData();
	data.append("id", (level==1 ? 0 : document.getElementById("cat1").value));

	// (A2) AJAX FETCH CATEGORIES
	fetch("3-ajax.php", { method: "POST", body: data })
	.then(res => res.json())
	.then(cat => {
	// (A2-1) UPDATE HTML SELECTOR
	let selector = document.getElementById("cat" + level);
	selector.innerHTML = "";
	for (let i in cat) {
	let opt = document.createElement("option");
	opt.value = i;
	opt.innerHTML = cat[i];
	selector.appendChild(opt);
	}

	// (A2-2) CASCADE LOAD SUB-CATEGORY
	if (level==1) { loadcat(2); }
	});
	}

	// (B) INIT LOAD
	window.onload = () => loadcat(1);
	/* (X) DOES NOT MATTER */
	* {
	font-family: Arial, Helvetica, sans-serif;
	box-sizing: border-box;
	}
	form {
	max-width: 400px;
	padding: 30px 20px;
	border: 1px solid #e1e1e1;
	background: #f2f2f2;
	}
	label, select {
	display: block;
	width: 100%;
	}
	label {
	margin: 10px 0;
	color: #4a4a4a;
	}
	form label:first-child { margin-top: 0; }
	select {
	padding: 10px;
	border: 1px solid #d5d5d5;
	}