Multiple keyword Search

function sps_custom_multiple_keyword_search( $search, $wp_query ) {

	$search_terms = $wp_query->get( 's' );
	$search_terms = trim( $search_terms );

	if ( empty( $search_terms ) ) {
		return $search;
	} 
	// Check if search query contains the "+" symbol
    if ( defined('DOING_AJAX') && DOING_AJAX && strpos( $search_terms, '+') !== false ) {
		$search_terms_array = explode( '+', $search_terms );
		$search_terms_array = array_map( 'trim', $search_terms_array );
		$search_terms_array = array_filter( $search_terms_array );

		if ( empty( $search_terms_array ) ) {
			return $search;
		}
		global $wpdb;
		$search_sql = array();
		foreach ( $search_terms_array as $term ) {
			$term        = esc_sql( $term );
			$search_sql[]= "({$wpdb->posts}.post_title LIKE '%{$term}%' OR {$wpdb->posts}.post_content LIKE '%{$term}%')";
		}

		if ( ! empty( $search_sql ) ) {
			$search_sql = implode( ' OR ', $search_sql );
			$search = " AND ({$search_sql})";
		}
	}

	return $search;
}
add_filter( 'posts_search', 'sps_custom_multiple_keyword_search', 10, 2 );