WP_Network_Query::get_search_sql( string $string, string[] $columns )

Source

File: wp-includes/class-wp-network-query.php

protected function get_search_sql( $string, $columns ) {
		global $wpdb;

		$like = '%' . $wpdb->esc_like( $string ) . '%';

		$searches = array();
		foreach ( $columns as $column ) {
			$searches[] = $wpdb->prepare( "$column LIKE %s", $like );
		}

		return '(' . implode( ' OR ', $searches ) . ')';
	}