What are best practices for defining the action attribute in a PHP form?

When defining the action attribute in a PHP form, it is best practice to set it to the current file name or the URL of the script that will handle the form submission. This ensures that the form data is sent to the correct location for processing. It is important to use the $_SERVER['PHP_SELF'] variable to dynamically set the action attribute to the current file name, as this helps prevent security vulnerabilities such as cross-site scripting attacks.

<form action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]); ?>" method="post">
  <!-- Form fields go here -->
</form>