(PECL solr >= 0.9.2)
SolrDocument::addField — Adds a field to the document
$fieldName, string $fieldValue): boolThis method adds a field to the SolrDocument instance.
fieldNameThe name of the field
fieldValueThe value of the field.
成功時(shí)返回 true， 或者在失敗時(shí)返回 false。