'sanitize_text_field' ] ); register_setting( 'adbkp_settings_group', 'adbkp_username', [ 'sanitize_callback' => 'sanitize_text_field' ] ); // Use sanitize callback for boolean (checkbox) register_setting( 'adbkp_settings_group', 'adbkp_sandbox_mode', [ 'sanitize_callback' => [ $this, 'sanitize_checkbox' ] ] ); register_setting( 'adbkp_settings_group', 'adbkp_password', [ 'sanitize_callback' => 'sanitize_text_field' ] ); register_setting( 'adbkp_settings_group', 'adbkp_app_key', [ 'sanitize_callback' => 'sanitize_text_field' ] ); } /** * Sanitize checkbox input. * * @param mixed $input Input value. * @return string Sanitized checkbox value. */ public function sanitize_checkbox( $input ) { return $input === '1' ? '1' : '0'; } /** * Render the settings page. */ public function render_settings_page() { ?>