Add gravity flow demo

backend/wordpress/wp-content/plugins/wp-mail-smtp/src/Admin/PageAbstract.php

@@ -0,0 +1,66 @@
+<?php
+
+namespace WPMailSMTP\Admin;
+
+/**
+ * Class PageAbstract.
+ *
+ * @since 1.0.0
+ */
+abstract class PageAbstract implements PageInterface {
+
+	/**
+	 * @var string Slug of a tab.
+	 */
+	protected $slug;
+
+	/**
+	 * @inheritdoc
+	 */
+	public function get_link() {
+		return esc_url(
+			add_query_arg(
+				'tab',
+				$this->slug,
+				admin_url( 'options-general.php?page=' . Area::SLUG )
+			)
+		);
+	}
+
+	/**
+	 * Process tab form submission ($_POST ).
+	 *
+	 * @since 1.0.0
+	 *
+	 * @param array $data $_POST data specific for the plugin.
+	 */
+	public function process_post( $data ) {
+	}
+
+	/**
+	 * Process tab & mailer specific Auth actions.
+	 *
+	 * @since 1.0.0
+	 */
+	public function process_auth() {
+	}
+
+	/**
+	 * Print the nonce field for a specific tab.
+	 *
+	 * @since 1.0.0
+	 */
+	public function wp_nonce_field() {
+		wp_nonce_field( Area::SLUG . '-' . $this->slug );
+	}
+
+	/**
+	 * Make sure that a user was referred from plugin admin page.
+	 * To avoid security problems.
+	 *
+	 * @since 1.0.0
+	 */
+	public function check_admin_referer() {
+		check_admin_referer( Area::SLUG . '-' . $this->slug );
+	}
+}