Change your code to this register_setting( ‘rex_plug_options’, ‘rex_plug_options’, ‘rex_plug_settings_validate’ ); add_settings_field(‘rex_plugbox_text_exit_pop_selected_pages’, ‘Select Pages’, ‘rex_plugbox_text_exit_pop_selected_pages’, ‘rex_plug_box’, ‘rex_plug_main_box’); //with selectbox you cannot select multiple pages. If you need that try checkbox function rex_plugbox_text_exit_pop_selected_pages(){ global $rex_plug_options; if(!isset($rex_plug_options[“rex_plugbox_text_exit_pop_selected_pages”])) { $rex_plug_options[“rex_plugbox_text_exit_pop_selected_pages”] = “”; } ?> <select id=”rex_plugbox_text_exit_pop_selected_pages” name=”rex_plug_options[rex_plugbox_text_exit_pop_selected_pages]”> <?php if( $pages = get_pages() ){ foreach( $pages as $page ){ echo … Read more