code: public function add_custom_profile_fields( $user ) {
  
  		$user_settings = apply_filters( 'iac_get_user_settings', array(), $user->ID );
  		$nonce         = wp_create_nonce( 'iac_user_settings' );
  	?>
  		<h3><?php _e( 'Informer?', $this->get_textdomain() ); ?></h3>
  
  		<table class="form-table">
  			<tr id="post_subscription">
  				<th>
  					<label for="post_subscription_checkbox"><?php _e( 'Posts subscription', $this->get_textdomain() ); ?></label>
  				</th>
  				<td>
  					<input type="checkbox" id="post_subscription_checkbox" name="post_subscription" value="1"
  					<?php checked( '1', $user_settings[ 'inform_about_posts' ] ); ?> />
  					<span class="description"><?php _e( 'Inform about new posts via e-mail, without your own posts.', $this->get_textdomain() ); ?></span>
  				</td>
  			</tr>
  			<tr id="comment_subscription">
  				<th>
  					<label for="comment_subscription_checkbox"><?php _e( 'Comments subscription', $this->get_textdomain() ); ?></label>
  				</th>
  				<td>
  					<input type="checkbox" id="comment_subscription_checkbox" name="comment_subscription" value="1"
  					<?php checked( '1', $user_settings[ 'inform_about_comments' ] ); ?> />
  					<span class="description"><?php _e( 'Inform about new comments via e-mail, without your own comments.', $this->get_textdomain() ); ?></span>
  					<input type="hidden" name="iac_nonce" value="<?php echo $nonce;?>" />
  				</td>
  			</tr>
  		</table>
  	<?php }
docs: Add cutom profile fields
  
  @wp-hook show_user_profile
  @wp-hook edit_user_profile
  
  @since  0.0.2
  @uses   _e, checked
  
  @param  array $user
  
  @return void