<?php
// 在 <head> 中加入 GTM 代碼
function add_gtm_head_script() {
    ?>
    <!— Google Tag Manager ⟶
    <script>
        (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':
        new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],
        j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src=
        'https://www.googletagmanager.com/gtm.js?id=' + i + dl;f.parentNode.insertBefore(j,f);
        })(window,document,'script','dataLayer','GTM-XXXXXX');
    </script>
    <!— End Google Tag Manager ⟶
    <?php
}
add_action('wp_head', 'add_gtm_head_script');

// 在 <body> 開頭後面加入 GTM 代碼
function add_gtm_body_script() {
    ?>
    <!— Google Tag Manager (noscript) ⟶
    <noscript>
        <iframe src="https://www.googletagmanager.com/ns.html?id=GTM-XXXXXX"
        height="0" width="0" style="display:none;visibility:hidden"></iframe>
    </noscript>
    <!— End Google Tag Manager (noscript) ⟶
    <?php
}
add_action('wp_body_open', 'add_gtm_body_script'); // 需 WordPress 5.2 以上版本支援

// 如果你的主題不支援 wp_body_open，改用以下方式
add_action('after_setup_theme', function() {
    if (!has_action('wp_body_open')) {
        add_action('wp_footer', 'add_gtm_body_script');
    }
});