让PHP函数使用全局变量作为默认值？

<?php
$globalVar = "global value";

function myFunction($param = null) {
    global $globalVar;
    if ($param === null) {
        $param = $globalVar;
    }
    echo "Parameter: " . $param . "\n";
}

myFunction(); // 输出: Parameter: global value
myFunction("custom value"); // 输出: Parameter: custom value
?>

<?php
$globalVar = "global value";

function myFunction($param = null) {
    $defaultParam = function() use ($globalVar) {
        return $globalVar;
    };
    $param = $param === null ? $defaultParam() : $param;
    echo "Parameter: " . $param . "\n";
}

myFunction(); // 输出: Parameter: global value
myFunction("custom value"); // 输出: Parameter: custom value
?>