Theme Option Wordpress - Banna

<?php
// create custom plugin settings menu
add_action('admin_menu', 'my_cool_plugin_create_menu');

function my_cool_plugin_create_menu() {

	//create new top-level menu
	add_menu_page('Google Ad', 'Google Ad Settings', 'administrator', __FILE__, 'my_cool_plugin_settings_page' , 'dashicons-screenoptions', __FILE__) );

	//call register settings function
	add_action( 'admin_init', 'register_my_cool_plugin_settings' );
}


function register_my_cool_plugin_settings() {
	//register our settings
	register_setting( 'my-cool-plugin-settings-group', 'core_google_ad' );
	
}

function my_cool_plugin_settings_page() {
?>
<div class="wrap">
<h1>Google Ad Settings</h1>

<form method="post" action="options.php">
    <?php settings_fields( 'my-cool-plugin-settings-group' ); ?>
    <?php do_settings_sections( 'my-cool-plugin-settings-group' ); ?>
    <table class="form-table">
        <tr valign="top">
        <th scope="row">Enter Advertisment Code</th>
        <td>
        <textarea name="core_google_ad">
        <?php echo esc_attr( get_option('core_google_ad') ); ?>
        </textarea>
       </td>
        <small> You can enter any advertisment code here </small>
        </tr>
         
    </table>
    
    <?php submit_button(); ?>

</form>
</div>
<?php } ?>