What are some key considerations for ensuring the security and stability of a PHP-based chat feature on a website?

Key considerations for ensuring the security and stability of a PHP-based chat feature on a website include implementing input validation to prevent SQL injection and cross-site scripting attacks, using secure encryption methods to protect sensitive data, and regularly updating PHP and any third-party libraries to patch security vulnerabilities.

// Example of input validation to prevent SQL injection
$user_message = mysqli_real_escape_string($connection, $_POST['message']);