What best practices should be followed when integrating PHP and JavaScript for interactive web applications?

When integrating PHP and JavaScript for interactive web applications, it's important to separate server-side logic (PHP) from client-side logic (JavaScript) to maintain a clean and organized codebase. One best practice is to use AJAX to asynchronously communicate between PHP and JavaScript, allowing for dynamic updates without refreshing the entire page. Additionally, consider using JSON to pass data between PHP and JavaScript for easier parsing and manipulation on both ends.

// PHP code snippet to handle AJAX request and return JSON response
if(isset($_POST['data'])){
    // Process data from JavaScript
    $result = processData($_POST['data']);
    
    // Return JSON response
    header('Content-Type: application/json');
    echo json_encode($result);
}

// Function to process data
function processData($data){
    // Perform necessary operations on data
    $processedData = $data * 2;
    
    return $processedData;
}