What are the security implications of using outdated PHP versions like PHP 4 in a production environment?

Using outdated PHP versions like PHP 4 in a production environment can pose significant security risks as these versions may have known vulnerabilities that can be exploited by attackers. To mitigate this risk, it is crucial to update to a supported PHP version that receives security patches and updates regularly.

// Example of updating PHP version in a production environment
// Replace PHP 4 with a supported PHP version like PHP 7.4

// Original code using PHP 4
echo "Hello, World!";