How can PHP developers handle input validation for special characters and line breaks in email forms effectively?

To handle input validation for special characters and line breaks in email forms effectively, PHP developers can use the `filter_var` function with the `FILTER_SANITIZE_EMAIL` filter to clean and validate email inputs. Additionally, they can use `preg_replace` to remove special characters and line breaks from the email input before further processing.

$email = $_POST['email'];

// Sanitize and validate email input
$email = filter_var($email, FILTER_SANITIZE_EMAIL);

// Remove special characters and line breaks
$email = preg_replace('/[^a-zA-Z0-9@._-]/', '', $email);

// Further processing of the sanitized email input
// e.g. sending email or saving to database