What are common pitfalls when using outdated PHP code?

Using outdated PHP code can lead to security vulnerabilities, compatibility issues, and decreased performance. To solve this problem, it is important to update your PHP version to a supported release and refactor any deprecated functions or features in your code.

// Example code snippet to update deprecated functions

// Before
mysql_connect('localhost', 'username', 'password');

// After
mysqli_connect('localhost', 'username', 'password');