In what scenarios should developers consider switching from ISO-8859-1 to UTF-8 encoding for PHP files to avoid character encoding issues?

Developers should consider switching from ISO-8859-1 to UTF-8 encoding for PHP files when they encounter character encoding issues, such as displaying special characters incorrectly or encountering encoding errors. UTF-8 encoding supports a wider range of characters and is more compatible with various languages and scripts, making it a better choice for multilingual applications.

// Set UTF-8 encoding in PHP files
header('Content-Type: text/html; charset=utf-8');