如何从子函数向父函数传递变量(Laravel)

function childFunction() {
    $variable = "Hello from child function";
    return $variable;
}

function parentFunction() {
    $result = childFunction();
    echo $result; // 输出：Hello from child function
}

parentFunction();

function childFunction(&$variable) {
    $variable = "Hello from child function";
}

function parentFunction() {
    $variable = "";
    childFunction($variable);
    echo $variable; // 输出：Hello from child function
}

parentFunction();

$variable = ""; // 全局变量

function childFunction() {
    global $variable;
    $variable = "Hello from child function";
}

function parentFunction() {
    global $variable;
    childFunction();
    echo $variable; // 输出：Hello from child function
}

parentFunction();