【WordPress】管理画面に自作管理メニューとサブメニューを追加する方法

add_action('admin_menu', 'my_admin_menu');
 
function my_admin_menu(){
	add_menu_page( 'myメニュー' , 'myメニュー' , 'manage_options' , 'my_menu'
			  , 'echo_my_menu' , '' , 3 );
}

add_action( 'admin_init', 'register_my_menu' );
 
function register_my_menu(){
    register_setting( 'my_option_group' , 'my_option_1' );
}

function echo_my_menu() {
	?>
	<div class="wrap">
		<h2>myメニュー</h2>
		<form method="post" action="options.php">
	<?php 
		settings_fields( 'my_option_group' );
	?>
		<table class="form-table">
		<tr><th scope="row" >項目１</th>
		<td>
		<?php $value = esc_textarea( get_option('my_option_1','') ); ?>
		<textarea id="my_option_1" name="my_option_1" cols="160" rows="7"><?= $value ?></textarea>
		</td></tr>
		</table>
		<?php submit_button(); ?>
		</form>
	</div>
<?php
}

add_action('admin_menu', 'my_admin_menu');

function my_admin_menu(){
	add_menu_page( 'myメニュー' , 'myメニュー' , 'manage_options' , 'my_menu'
			  , 'echo_my_menu' , '' , 3 );
}

add_action( 'admin_init', 'register_my_menu' );

function register_my_menu(){
    register_setting( 'my_option_group' , 'my_option_1' );
}

function echo_my_menu() {
	?>
	<div class="wrap">
		<h2>myメニュー</h2>
		<form method="post" action="options.php">
	<?php 
		settings_fields( 'my_option_group' );
	?>
		<table class="form-table">
		<tr><th scope="row" >項目１</th>
		<td>
		<?php $value = esc_textarea( get_option('my_option_1','') ); ?>
		<textarea id="my_option_1" name="my_option_1" cols="160" rows="7"><?= $value ?></textarea>
		</td></tr>
		</table>
		<?php submit_button(); ?>
		</form>
	</div>
<?php
}

add_action('admin_menu', 'my_admin_menu_sub');

function my_admin_menu_sub(){
	add_submenu_page( 'my_menu' , 'subメニュー' , 'subメニュー' , 'manage_options' , 'my_sub_menu'
			  , 'echo_my_sub_menu' , '' );
}

add_action( 'admin_init', 'register_my_menu_sub' );
     
function register_my_menu_sub(){
    register_setting( 'my_sub_option_group' , 'my_sub_option_1' ); // サブメニュー
}

function echo_my_sub_menu() {
	?>
	<div class="wrap">
		<h2>myメニュー</h2>
		<form method="post" action="options.php">
	<?php 
		settings_fields( 'my_sub_option_group' );
	?>
		<table class="form-table">
		<tr><th scope="row" >項目１</th>
		<td>
		<?php $value = esc_textarea( get_option('my_sub_option_1','') ); ?>
		<textarea id="my_sub_option_1" name="my_sub_option_1" cols="160" rows="7"><?= $value ?></textarea>
		</td></tr>
		</table>
		<?php submit_button(); ?>
		</form>
	</div>
<?php
}

■【WordPress】管理画面に追加した項目の値を検証してエラー出力する方法

add_action('admin_menu', function() {
	$menu_slug = 'my_setting_menu';
	$data = array(
		'title' => 'My設定',
		'option_group' => 'my_setting_menu_group',
		'option_data' => array(
			array( 'name'=>'my_opt1' , 'title'=>'設定1' , 'type'=>'textarea' , 'value'=>'' , 'description'=>'' ),
			array( 'name'=>'my_opt2' , 'title'=>'設定2' , 'type'=>'checkbox' , 'value'=>'1' , 'description'=>'チェック' ),
			array( 'name'=>'my_opt3' , 'title'=>'設定3' , 'type'=>'select'   , 'value'=>'cat,dog,panda' , 'description'=>'猫,犬,ぱんだ' ),
		)
	);
		// メニュー登録
	add_menu_page($data['title'], $data['title'], 'manage_options' , $menu_slug
			  , function() use($data){ echo_my_setting_menu($data); },'',3);

	add_action( 'admin_init',
			function() use($data){ register_my_setting_menu($data);});
},98);

	// 設定項目を登録
function register_my_setting_menu($data){

	foreach( $data['option_data'] as $option_data){
		register_setting( $data['option_group'], $option_data['name'] );
	}

}

	// 管理画面の表示
function echo_my_setting_menu($data) {
	?>
	<div class="wrap">
		<h2><?php echo $data['title']; ?></h2>
			<form method="post" action="options.php">
	<?php 
			settings_fields( $data['option_group'] );
	?>
			<table class="form-table">
	<?php
				foreach($data['option_data'] as $option_data){
					echo '<tr><th scope="row" >'.$option_data['title'].'</th><td>';

					$id = $option_data['name'];

					switch( $option_data['type'] ){

					case 'textarea':

						echo '<textarea id="'.$id.'" name="'.$id.'" cols="160" rows="7">'
							.esc_textarea( get_option($id,$option_data['value'])).'</textarea>';
						break;

					case 'checkbox':

						$value = $option_data['value'];
						$checked = get_option($id,'') === $value ? ' checked' : '';
						echo '<input type="checkbox" id="'.$id.'" name="'.$id.'" value="'.$value.'"'.$checked.'>'
								.$option_data['description'].'</label>';
						break;

					case 'select':

						$values = explode(',', $option_data['value']);
						$descriptions = explode(',', $option_data['description']);
						$current_value = get_option($id,'');
						if( !in_array($current_value,$values) ) $current_value = $values[0];

						echo '<select id="'.$id.'" name="'.$id.'">';
						foreach( $values as $index => $v ){
							$selected = $current_value === $v ? ' selected' : '';
							echo '<option value="'.$v.'"'.$selected.'>'.$descriptions[$index].'</option>';
						}
						echo '</select>';
						break;
					}
					echo '</td></tr>';
				}
	  ?>
		</table>
		<?php submit_button(); ?>
	</form>
	</div>
	<?php
}