how to save a select option dropdown in a wordpress plugin

Use this function this is just an example to save a select option dropdown in a wordpress plugin you can use it as per your needed.

Example 1

class DropdownOptionSetting {    private $dropdown_option_setting_options;    public function __construct() {        add_action( 'admin_menu', array( $this, 'dropdown_option_setting_add_plugin_page' ) );        add_action( 'admin_init', array( $this, 'dropdown_option_setting_page_init' ) );    }    public function dropdown_option_setting_add_plugin_page() {        add_options_page(            'Dropdown Option Setting', // page_title            'Dropdown Option Setting', // menu_title            'manage_options', // capability            'dropdown-option-setting', // menu_slug            array( $this, 'dropdown_option_setting_create_admin_page' ) // function        );    }    public function dropdown_option_setting_create_admin_page() {        $this->dropdown_option_setting_options = get_option( 'dropdown_option_setting_option_name' ); ?>        <div class="wrap">            <h2>Dropdown Option Setting</h2>            <p></p>            <?php settings_errors(); ?>            <form method="post" action="options.php">                <?php                    settings_fields( 'dropdown_option_setting_option_group' );                    do_settings_sections( 'dropdown-option-setting-admin' );                    submit_button();                ?>            </form>        </div>    <?php }    public function dropdown_option_setting_page_init() {        register_setting(            'dropdown_option_setting_option_group', // option_group            'dropdown_option_setting_option_name', // option_name            array( $this, 'dropdown_option_setting_sanitize' ) // sanitize_callback        );        add_settings_section(            'dropdown_option_setting_setting_section', // id            'Settings', // title            array( $this, 'dropdown_option_setting_section_info' ), // callback            'dropdown-option-setting-admin' // page        );        add_settings_field(            'dropdown_option_0', // id            'Dropdown Option', // title            array( $this, 'dropdown_option_0_callback' ), // callback            'dropdown-option-setting-admin', // page            'dropdown_option_setting_setting_section' // section        );    }    public function dropdown_option_setting_sanitize($input) {        $sanitary_values = array();        if ( isset( $input['dropdown_option_0'] ) ) {            $sanitary_values['dropdown_option_0'] = $input['dropdown_option_0'];        }        return $sanitary_values;    }    public function dropdown_option_setting_section_info() {    }    public function dropdown_option_0_callback() {        ?> <select name="dropdown_option_setting_option_name[dropdown_option_0]" id="dropdown_option_0">            <?php $selected = (isset( $this->dropdown_option_setting_options['dropdown_option_0'] ) && $this->dropdown_option_setting_options['dropdown_option_0'] === 'option-one') ? 'selected' : '' ; ?>            <option value="option-one" <?php echo $selected; ?>>Option One</option>            <?php $selected = (isset( $this->dropdown_option_setting_options['dropdown_option_0'] ) && $this->dropdown_option_setting_options['dropdown_option_0'] === 'option-two') ? 'selected' : '' ; ?>            <option value="option-two" <?php echo $selected; ?>>Option Two</option>            <?php $selected = (isset( $this->dropdown_option_setting_options['dropdown_option_0'] ) && $this->dropdown_option_setting_options['dropdown_option_0'] === 'option-three') ? 'selected' : '' ; ?>            <option value="option-three" <?php echo $selected; ?>>Option Three</option>        </select> <?php    }}if ( is_admin() )    $dropdown_option_setting = new DropdownOptionSetting();

Retrieve this value

$dropdown_option = get_option( 'dropdown_option_setting_option_name' ); // Array$dropdown_value =  $dropdown_option ['dropdown_option_0']; // Option value

If you need a simple way to do this

Example 2

add_action( 'admin_init', 'Dropdown_settings_init' );function Dropdown_settings_init(  ) {     register_setting( 'pluginPage', 'dropdown_settings' );    add_settings_section(        'Dropdown_pluginPage_section',         __( 'Your section description', 'dropdown' ),         'Dropdown_settings_section_callback',         'pluginPage'    );    add_settings_field(         'select_field_0',         __( 'Settings field description', 'dropdown' ),         'Dropdown_select_field_render',         'pluginPage',         'Dropdown_pluginPage_section'     );}function Dropdown_select_field_render(  ) {     $options = get_option( 'dropdown_settings' );    ?>    <select name='dropdown_settings[select_field_0]'>        <option value='1' <?php selected( $options['select_field_0'], 1 ); ?>>Option 1</option>        <option value='2' <?php selected( $options['select_field_0'], 2 ); ?>>Option 2</option>        <option value='3' <?php selected( $options['select_field_0'], 3 ); ?>>Option 3</option>        <option value='4' <?php selected( $options['select_field_0'], 4 ); ?>>Option 4</option>    </select><?php}function Dropdown_settings_section_callback(  ) {     echo __( 'This section description', 'dropdown' );}function Dropdown_options_page(  ) {     ?>    <form action='options.php' method='post'>        <h2>Dropdown</h2>        <?php        settings_fields( 'pluginPage' );        do_settings_sections( 'pluginPage' );        submit_button();        ?>    </form>    <?php}?>