【WordPress】投稿ページや固定ページの各記事ごとに個別のCSSやJavaScriptの入力エリアを設ける方法「備忘録」

WordPressの「functions.php」を触って、入力エリアを設ける。※「functions.php」は極力触りたくないが、プラグインを導入をなるべく行いたくないので。

CSS

//記事内CSS入力エリア

add_action( 'admin_menu', 'custom_css_hooks' );
add_action( 'save_post', 'save_custom_css' );
add_action( 'wp_head','insert_custom_css' );
function custom_css_hooks() {
 add_meta_box( 'custom_css', 'Custom CSS', 'custom_css_input', 'post', 'normal', 'high' );
 add_meta_box( 'custom_css', 'Custom CSS', 'custom_css_input', 'page', 'normal', 'high' );
}
function custom_css_input() {
 global $post;
 echo '<input type="hidden" name="custom_css_noncename" id="custom_css_noncename" value="'.wp_create_nonce('custom-css').'" />';
 echo '<textarea name="custom_css" id="custom_css" rows="5" cols="30" style="width:100%;">'.get_post_meta($post->ID,'_custom_css',true).'</textarea>';
}
function save_custom_css($post_id) {
 if ( !wp_verify_nonce( $_POST['custom_css_noncename'], 'custom-css' ) ) return $post_id;
 if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE) return $post_id;
 $custom_css = $_POST['custom_css'];
 update_post_meta( $post_id, '_custom_css', $custom_css );
}
function insert_custom_css() {
 if ( is_page() || is_single() ) {
   if ( have_posts() ) : while ( have_posts() ) : the_post();
     echo '<style type="text/css">' . get_post_meta(get_the_ID(), '_custom_css', true) . '</style>';
   endwhile; endif;
   rewind_posts();
 }
}

JavaScript

//記事内JavaScript入力エリア

add_action( 'admin_menu', 'custom_js_hooks' );
add_action( 'save_post', 'save_custom_js' );
add_action( 'wp_head','insert_custom_js' );
function custom_js_hooks() {
 add_meta_box( 'custom_js', 'Custom JS', 'custom_js_input', 'post', 'normal', 'high' );
 add_meta_box( 'custom_js', 'Custom JS', 'custom_js_input', 'page', 'normal', 'high' );
}
function custom_js_input() {
 global $post;
 echo '<input type="hidden" name="custom_js_noncename" id="custom_js_noncename" value="'.wp_create_nonce('custom-js').'" />';
 echo '<textarea name="custom_js" id="custom_js" rows="5" cols="30" style="width:100%;">'.get_post_meta($post->ID,'_custom_js',true).'</textarea>';
}
function save_custom_js($post_id) {
 if (!wp_verify_nonce($_POST['custom_js_noncename'], 'custom-js')) return $post_id;
 if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) return $post_id;
 $custom_js = $_POST['custom_js'];
 update_post_meta($post_id, '_custom_js', $custom_js);
}
function insert_custom_js() {
 if ( is_page() || is_single() ) {
   if ( have_posts() ) : while ( have_posts() ) : the_post();
     echo '<script type="text/javascript">' . get_post_meta(get_the_ID(), '_custom_js', true) . '</script>';
   endwhile; endif;
   rewind_posts();
 }
}

https://youtu.be/_X6QCqb7kNA

リファレンス：https://digwp.com/2010/02/custom-css-per-post/