Use Elementor to power SearchWP Supplemental Engine

functions.php

<?php

// @link https://searchwp.com/v3/docs/kb/using-elementor-for-supplemental-engines/



// We need to flag the search form.
add_action( 'elementor_pro/search_form/after_input', function( $form ) {
	// Check to see if this is the right Search Form.
	$settings = $form->get_data( 'settings' );
	
	if ( isset( $settings['_element_id'] ) && 'searchwp-supplemental-form' == $settings['_element_id'] ) {
		?>
		<input type="hidden" name="searchwp" value="supplemental" />
		<?php
	}
} );

// Redirect when applicable.
add_action( 'template_redirect', function() {
	if ( is_search() && ! empty( $_GET['searchwp'] ) && 'supplemental' === $_GET['searchwp'] ) {
		wp_safe_redirect( add_query_arg( array(
			'swpquery' => get_search_query(),
		), get_permalink( 18 ) ) );
		exit();
	}
} );

// Provide Search results.
add_filter( 'elementor/query/query_args', function( $query_vars, $widget ) {
	// Check to see if this is the right Widget.
	$settings = $widget->get_data( 'settings' );

	if ( is_admin()
		|| ! isset( $settings['posts_query_id'] )
		|| ( ! empty( $settings['posts_query_id'] ) && 'searchwp-supplemental' !== $settings['posts_query_id'] ) ) {
		return $query_vars;
	}

	// This form field was set up in Elementor.
	$query = isset( $_GET['swpquery'] ) ? sanitize_text_field( $_GET['swpquery'] ) : '';

	if ( ! empty( $query ) ) {
		// Perform the search.
		$searchwp = new SWP_Query( array(
			's'              => $query,
			'engine'         => 'supplemental', // Engine to search.
			'fields'         => 'ids',
			'posts_per_page' => -1,
		) );

		if ( empty( $searchwp->posts ) ) {
			$searchwp->posts = array( 0 );
		}

		// Override the query vars with SearchWP results.
		$query_vars['post__in']    = $searchwp->posts;
		$query_vars['post_type']   = 'any';      // Restricted by post__in.
		$query_vars['post_status'] = 'any';      // Restricted by post__in.
		$query_vars['orderby']     = 'post__in'; // Order by post__in.
		$query_vars['order']       = 'DESC';     // Order descending.
	} else {
		// Force no results.
		$query_vars['post__in'] = array( 0 );
	}

	return $query_vars;
}, 10, 2 );