How can the PHP variable scope impact the access and manipulation of variables in included PHP files within a larger PHP script?

The PHP variable scope can impact the access and manipulation of variables in included PHP files within a larger PHP script because included files inherit the variable scope of the parent file. To ensure that variables are accessible and manipulable in included files, you can use global variables or pass variables as parameters to functions defined in the included files.

// parent.php
$var = 'Hello';

function manipulateVar() {
    global $var;
    echo $var . ' World';
}

include 'child.php';

manipulateVar();
```

```php
// child.php
manipulateVar();