Use jQuery, it'll help you forget about browsers and focus on coding alone.
Assume this is your HTML and Javascript
<html>
<head>
<title>Dropdowns</title>
<script type="text/javascript" src="http://code.jquery.com/jquery-latest.min.js"></script>
<script type="text/javascript">
$(document).ready(function() {
// Detect if a change to the name dropdown is made
$("#name").change(function() {
// Setup the AJAX call (this is a call which expects JSON as response)
$.ajax({
url: "http://example.com/api.php",
type: "json",
// Specify the GET parameter "name" with the value from the name dropdown
data: {
name: $("#name").val()
},
// If AJAX was successfull add the regarding values to the date dropdown
success: function() {
// The response from PHP contains an array encoded in JSON.
// This means, we have to loop trough the results
$.each(data.directors, function() {
$("#date").append(
// This actually appends the value on the date dropdown
$("<option></option>").val(this.value).html(this.label)
)
});
}
});
// Detect if a change to the date dropdown is made
$("#date").change(function() {
// Setup the AJAX call (this is a call which expects JSON as response)
$.ajax({
url: "http://example.com/api.php",
type: "json",
// Specify the GET parameter "date" with the value from the date dropdown
data: {
date: $("#date").val()
},
// If AJAX was successfull add the regarding values to the path dropdown
success: function() {
// The response from PHP contains an array encoded in JSON. This means, we have to loop trough the results
$.each(data.directors, function() {
$("#path").append(
// This actually appends the value on the path dropdown
$("<option></option>").val(this.value).html(this.label);
)
});
}
});
</script>
</head>
<body>
<form name="someform">
<select name="name" id="name">
<option value="1">John Smith</option>
<option value="2">Peter Johnson</option>
</select>
<select name="date" id="data">
<option value=""></option>
</select>
<select name="path" id="data">
<option value=""></option>
</select>
</form>
</body>
</html>
You'd need a PHP file, which outputs the data like the following:
<?php
if($_GET['name'] != "" && isset($_GET['name'])) {
// Now you'd need some logic to generate an array, containing the information for this name
// We'll just create one manually now
$dates = array();
$dates[]['value'] = "349876973";
$dates[]['label'] = "Date description 1";
$dates[]['value'] = "783693876";
$dates[]['label'] = "Date description 2";
echo json_encode($dates);
} elseif($_GET['date'] != "" && isset($_GET['date'])) {
// Now you'd need some logic to generate an array, containing the information for this date
// We'll just create one manually now
$paths = array();
$dates[]['value'] = "path value 1";
$dates[]['label'] = "Path description 1";
$dates[]['value'] = "path value 2";
$dates[]['label'] = "Path description 2";
echo json_encode($paths);
}
I couldn't test it, but hopefully it gives you an idea on AJAX and jQuery. Also have a look at jQuery Documentations and the API reference, which explains available methods and options.
Update: You're not bound to use value and label as the array key name. But if you want to, you could create a query which looks like this (this is a PDO example, you might want to get into PDO, since it saves you the hassle of escaping input, and makes recurring queries easier). This will require the PDO functions for PHP, which might be already installed if you're on a hoster.
includes/db.include.php
<?php
class example {
// Create database connection
public function __construct() {
$this->db = new PDO("pgsql:host=localhost;dbname=exampledb;", "user", "password");
if(!$this->db) {
die("Connection failed!");
}
}
// Get dates
public function getDates($name) {
$sql = "SELECT
date AS value, datedescription AS label
FROM
some_table
WHERE
name = ?";
$stmt = $this->db->prepare($sql);
$stmt->bindParam(1, $name);
if(!$stmt->execute()) {
// Only for debugging, wouldn't use this on production
var_dump($stmt->errorInfo());
}
$result = $stmt->fetchAll(PDO::FETCH_ASSOC);
return $result;
}
// Get paths
public function getPaths($date) {
$sql = "SELECT
path AS value, pathdescription AS label
FROM
another_table
WHERE
date = ?";
$stmt = $this->db->prepare($sql);
$stmt->bindParam(1, $date);
if(!$stmt->execute()) {
// Only for debugging, wouldn't use this on production
var_dump($stmt->errorInfo());
}
$result = $stmt->fetchAll(PDO::FETCH_ASSOC);
return $result;
}
// Close database connection
public function __destruct() {
@$this->db->close();
}
}
?>
And in your api.php you'd go like this
<?php
include 'includes/db.include.php';
$example = new example;
if(isset($_GET['name'])) {
echo json_encode($example->getDates($_GET['name']));
} elseif(isset($_GET['date'])) {
echo json_encode($example->getPaths());
}
But as I said, you might also change the jQuery code, so your columns don't have to be named value and label. Assuming you're table columns for the date are called "date" and "datedescription", you'd just use this code
$.each(data.directors, function() {
$("#date").append(
// This actually appends the value on the date dropdown
$("<option></option>").val(this.date).html(this.datedescription)
)
})
