What are best practices for including external libraries like PEAR in PHP scripts?

When including external libraries like PEAR in PHP scripts, it is best practice to use the `require_once` or `include_once` functions to ensure that the library is only included once to prevent conflicts. Additionally, it is recommended to use the full path to the library file to avoid any file path resolution issues.

// Include PEAR library using require_once with full path
require_once '/path/to/PEAR/PEAR.php';