What are common causes of the "Parse error: syntax error, unexpected T_INCLUDE" message in PHP scripts?

The "Parse error: syntax error, unexpected T_INCLUDE" message in PHP scripts typically occurs when there is a syntax error in the code related to including files using the include or require functions. This error can be solved by checking for any missing parentheses, semicolons, or quotes in the include statement, ensuring that the file path is correct, and verifying that the included file exists.

// Incorrect include statement causing syntax error
include 'header.php';
```

```php
// Correct include statement with proper syntax
include('header.php');