(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
fieldThe name of the backup field
field_overrideThe name of the field we are overriding this setting for.
Returns the current SolrQuery object, if the return value is used.