如何将PHP变量传递给JavaScript？

<?php
$phpVariable = "Hello, World!";
?>

<script>
    var jsVariable = '<?php echo $phpVariable; ?>';
    console.log(jsVariable);
</script>

<?php
$phpVariable = "Hello, World!";
$jsonVariable = json_encode($phpVariable);
?>

<script>
    var jsVariable = JSON.parse('<?php echo $jsonVariable; ?>');
    console.log(jsVariable);
</script>

<?php
$phpVariable = "Hello, World!";
?>

<script>
    var xhr = new XMLHttpRequest();
    xhr.onreadystatechange = function() {
        if (xhr.readyState === 4 && xhr.status === 200) {
            var jsVariable = xhr.responseText;
            console.log(jsVariable);
        }
    };
    xhr.open("GET", "get_php_variable.php?variable=<?php echo $phpVariable; ?>", true);
    xhr.send();
</script>