What are some potential pitfalls when using outdated resources, such as tutorials or manuals, for learning PHP?

Using outdated resources for learning PHP can lead to errors, security vulnerabilities, and deprecated functions being used. To avoid these pitfalls, it is crucial to refer to up-to-date documentation and tutorials to ensure you are following best practices and utilizing the latest features of PHP.

// Example of using an outdated function (mysql_query) that should be replaced with mysqli_query

// Outdated code
$result = mysql_query("SELECT * FROM users");

// Updated code using mysqli
$conn = mysqli_connect("localhost", "username", "password", "database");
$result = mysqli_query($conn, "SELECT * FROM users");