(PECL solr >= 0.9.2)
SolrQuery::setHighlightAlternateField — Specifies the backup field to use
If a snippet cannot be generated because there were no matching terms, one can specify a field to use as the backup or default summary
The name of the backup field
The name of the field we are overriding this setting for.
Returns the current SolrQuery object, if the return value is used.