<?php
// PHP代码
$getParam = isset($_GET['param']) ? $_GET['param'] : 'default';
?>

<script>
// JavaScript代码
var jsVar = "<?php echo $getParam; ?>";
console.log(jsVar);
</script>

<?php
$getData = $_GET; // 获取所有GET参数
?>

<script>
var jsData = <?php echo json_encode($getData); ?>;
console.log(jsData);
</script>

<div id="data-container" data-param="<?php echo htmlspecialchars($_GET['param']); ?>"></div>

<script>
var param = document.getElementById('data-container').dataset.param;
console.log(param);
</script>

<script>
var jsVar = <?php echo json_encode($_GET['param']); ?>;
</script>

$param = isset($_GET['param']) ? $_GET['param'] : null;

var decodedParam = decodeURIComponent(jsVar);