【WordPress】head内・bodyタグ直後・直前にコードを挿入する方法｜wp_body_openも解説

function my_custom_code_in_head() {
    ?>
    <script src="https://example.com/script.js"></script>
    <link rel="stylesheet" href="https://example.com/styles.css">
    <?php
}
add_action( 'wp_head', 'my_custom_code_in_head' );

add_action( 'wp_head', 'my_custom_code_in_head', 5 ); // 既定の10より早く出力

function my_custom_code_after_body_open() {
    ?>
    <!-- Google Tag Manager (noscript) など、bodyの直後に置きたいコード -->
    <?php
}
add_action( 'wp_body_open', 'my_custom_code_after_body_open' );

function my_custom_code_before_closing_body() {
    ?>
    <script src="https://example.com/footer-script.js"></script>
    <?php
}
add_action( 'wp_footer', 'my_custom_code_before_closing_body' );

<?php
/*
Plugin Name: Custom Code Inserter
Description: Insert custom code into head, after body, and footer.
Version: 1.0
*/

add_action( 'wp_head', function () {
    ?>
    <script src="https://example.com/script.js"></script>
    <?php
} );

add_action( 'wp_body_open', function () {
    ?>
    <!-- bodyの直後に置きたいコード -->
    <?php
} );

add_action( 'wp_footer', function () {
    ?>
    <script src="https://example.com/footer-script.js"></script>
    <?php
} );