is_ios example

wp_user_settings();
_wp_admin_html_begin();

$body_class = 'wp-core-ui wp-customizer js';

if ( wp_is_mobile() ) :
    $body_class .= ' mobile';
    add_filter( 'admin_viewport_meta', '_customizer_mobile_viewport_meta' );
endif;

if ( $wp_customize->is_ios() ) {
    $body_class .= ' ios';
}

if ( is_rtl() ) {
    $body_class .= ' rtl';
}
$body_class .= ' locale-' . sanitize_html_class( strtolower( str_replace( '_', '-', get_user_locale() ) ) );

if ( wp_use_widgets_block_editor() ) {
    $body_class .= ' wp-embed-responsive';
}

'return'        => sanitize_url( $this->get_return_url() ),
                'parent'        => sanitize_url( admin_url() ),
                'activated'     => sanitize_url( home_url( '/' ) ),
                'ajax'          => sanitize_url( admin_url( 'admin-ajax.php', 'relative' ) ),
                'allowed'       => array_map( 'sanitize_url', $this->get_allowed_urls() ),
                'isCrossDomain' => $this->is_cross_domain(),
                'home'          => sanitize_url( home_url( '/' ) ),
                'login'         => sanitize_url( $login_url ),
            ),
            'browser'                => array(
                'mobile' => wp_is_mobile(),
                'ios'    => $this->is_ios(),
            ),
            'panels'                 => array(),
            'sections'               => array(),
            'nonce'                  => $this->get_nonces(),
            'autofocus'              => $this->get_autofocus(),
            'documentTitleTmpl'      => $this->get_document_title_template(),
            'previewableDevices'     => $this->get_previewable_devices(),
            'l10n'                   => array(
                'confirmDeleteTheme'   => __( 'Are you sure you want to delete this theme?' ),
                /* translators: %d: Number of theme search results, which cannot currently consider singular vs. plural forms. */
                'themeSearchResults'   => __( '%d themes found' ),