Why is it not recommended to rely on references for primitive data types in PHP?

Relying on references for primitive data types in PHP can lead to unexpected behavior and make the code harder to maintain. It is recommended to avoid using references for primitive data types to ensure clarity and consistency in the code.

// Avoid using references for primitive data types
$number = 10;
$reference = &$number;
$reference = 20;

echo $number; // Output: 20
```

Instead, you can simply work with the primitive data types directly without using references:

```php
// Use primitive data types directly
$number = 10;
$copy = $number;
$copy = 20;

echo $number; // Output: 10