What are the implications of passing variables by reference in PHP, especially when dealing with static strings or class objects?

Passing variables by reference in PHP can lead to unexpected behavior when dealing with static strings or class objects. To avoid this issue, it is recommended to pass variables by value instead of by reference, especially when dealing with immutable data like static strings or class objects.

// Example of passing variables by value instead of by reference
$staticString = "Hello, world!";
$copyOfString = $staticString; // Passing by value

class MyClass {
    public $property = "value";
}

$object = new MyClass();
$copyOfObject = clone $object; // Passing by value