What is the importance of using quotation marks when specifying file names in PHP scripts?

Using quotation marks when specifying file names in PHP scripts is important because it ensures that the file names are treated as strings. This is necessary when working with file functions such as include, require, fopen, etc., as PHP needs to know that the file name is a string to locate and manipulate the file correctly.

// Incorrect way of specifying file name without quotation marks
$file = example.txt;
```

```php
// Correct way of specifying file name with quotation marks
$file = "example.txt";