In PHP programming, what are the implications of passing references versus returning values in class methods for data access control?

When passing references in class methods, you are allowing direct access to the data, which can potentially lead to unintended modifications outside of the class. On the other hand, returning values allows for better data access control as the class can control what data is exposed and how it is manipulated.

<?php

class DataControl {
    private $data;

    public function setData($value) {
        $this->data = $value;
    }

    // Passing reference
    public function getDataByReference(&$value) {
        $value = $this->data;
    }

    // Returning value
    public function getData() {
        return $this->data;
    }
}

$dataControl = new DataControl();
$dataControl->setData("Hello World");

// Using passing reference
$referenceData = "";
$dataControl->getDataByReference($referenceData);
echo $referenceData . "\n"; // Output: Hello World

// Using returning value
$returnedData = $dataControl->getData();
echo $returnedData . "\n"; // Output: Hello World
?>