How can PHP developers ensure that their code is adaptable and can be easily modified for different hosting environments?

PHP developers can ensure that their code is adaptable and easily modified for different hosting environments by using configuration files to store environment-specific settings such as database credentials, API keys, and server paths. By centralizing these settings in a separate file, developers can easily make changes without modifying the main codebase. Additionally, using environment variables or constants to define paths and URLs can make the code more portable and easier to maintain.

```php
// config.php
define('DB_HOST', 'localhost');
define('DB_USER', 'username');
define('DB_PASS', 'password');
define('DB_NAME', 'database_name');
```
This code snippet demonstrates how to define database credentials in a separate configuration file, making it easy to modify these settings for different hosting environments.