How can PHP developers ensure that email addresses are externally valid before processing them in scripts?

To ensure that email addresses are externally valid before processing them in scripts, PHP developers can use the built-in filter_var function with the FILTER_VALIDATE_EMAIL filter. This function will check if the email address is in a valid format according to RFC 5322 standards. By validating email addresses before processing them, developers can prevent errors and security vulnerabilities in their scripts.

$email = "test@example.com";

if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
    // Email address is valid, proceed with processing
    echo "Email address is valid";
} else {
    // Email address is not valid, handle accordingly
    echo "Email address is not valid";
}