(PECL solr >= 0.9.2)
SolrQuery::setHighlightMaxAlternateFieldLength — Sets the maximum number of characters of the field to return
$fieldLength
   [, string $field_override
  ] )
   If SolrQuery::setHighlightAlternateField() was passed the value TRUE, this parameter specifies the maximum number of characters of the field to return
  
Any value less than or equal to 0 means unlimited.
fieldLengthThe length of the field
field_overrideThe name of the field.
Returns the current SolrQuery object, if the return value is used.