What are some best practices for including external JavaScript files in a PHP file for proper functionality on different servers?

When including external JavaScript files in a PHP file for proper functionality on different servers, it is important to use the correct path that works universally across different environments. One way to achieve this is by using the $_SERVER['DOCUMENT_ROOT'] variable to get the root directory of the server and then concatenate it with the relative path to the JavaScript file. 

<?php
$js_file_path = $_SERVER['DOCUMENT_ROOT'] . '/path/to/external.js';
echo "<script src='$js_file_path'></script>";
?>

Keywords

PHP JavaScript external files server compatibility include statement

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