Why is it recommended not to apply htmlspecialchars to data before storing it in a database in PHP?

It is not recommended to apply htmlspecialchars to data before storing it in a database because it can lead to issues when retrieving and displaying the data later on. It is better to store the raw data in the database and only apply htmlspecialchars when outputting the data to prevent double encoding.

// Storing data in the database without applying htmlspecialchars
$data = $_POST['data'];
// Store $data in the database without any modifications
```
When displaying the data:
```php
// Retrieving data from the database
$data = $row['data'];
// Output the data with htmlspecialchars to prevent XSS attacks
echo htmlspecialchars($data);