How can PHP developers ensure that data displayed in a form is specific to the selected option from a dropdown list populated from a database query?

When a user selects an option from a dropdown list populated from a database query, PHP developers can ensure that the data displayed in a form is specific to the selected option by using AJAX to dynamically fetch and display the relevant data based on the selected option. This can be achieved by creating a JavaScript function that triggers an AJAX request to a PHP script, which then queries the database for the specific data related to the selected option and returns it to the front end for display. 

// HTML form with a dropdown list
<form>
    <select id="dropdown" onchange="getData()">
        <option value="1">Option 1</option>
        <option value="2">Option 2</option>
    </select>
    <div id="data"></div>
</form>

// JavaScript function to fetch data based on selected option
<script>
function getData() {
    var selectedOption = document.getElementById("dropdown").value;
    var xhr = new XMLHttpRequest();
    xhr.onreadystatechange = function() {
        if (xhr.readyState === XMLHttpRequest.DONE) {
            if (xhr.status === 200) {
                document.getElementById("data").innerHTML = xhr.responseText;
            }
        }
    };
    xhr.open("GET", "get_data.php?option=" + selectedOption, true);
    xhr.send();
}
</script>

// PHP script (get_data.php) to query database and return specific data
<?php
$option = $_GET['option'];
// Perform database query based on selected option and fetch relevant data
echo $relevantData;
?>

Keywords

PHP dropdown list database query dynamic form data filtering

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