functions.php

<?php

// // ***** UNCOMMENT THIS IF YOU WANT TO USE SHORTCODES IN WIDGETS
// add_filter( 'widget_text', 'do_shortcode' );

// Output a SearchWP Engines dropdown
function my_searchwp_shortcodes_inject_engines() { ?>
	<p class="searchwp-shortcodes-engines">
		<?php
			$engines = SWP()->settings['engines'];
			$current_engine = isset( $_GET['swpengine'] ) ? esc_attr( $_GET['swpengine'] ) : 'default';
		?>
		<select name="swpengine" id="swpengine">
			<?php foreach ( $engines as $engine => $engine_settings ) : ?>
				<option value="<?php echo esc_attr( $engine ); ?>"
					<?php selected( $current_engine, $engine ); ?>>
					<?php echo isset( $engine_settings['searchwp_engine_label'] ) ? esc_html( $engine_settings['searchwp_engine_label'] ) : 'Default'; ?>
				</option>
			<?php endforeach; ?>
		</select>
	</p><?php
}

add_action( 'searchwp_shortcodes_after_input', 'my_searchwp_shortcodes_inject_engines' );