public SolrUpdateResponse SolrClient::commit    ([ bool $softCommit = FALSE   [, bool $waitSearcher = TRUE   [, bool $expungeDeletes = FALSE  ]]] )

SolrClient::commitFinalizes all add/deletes made to the index

softCommit

This will refresh the 'view' of the index in a more performant manner, but without "on-disk" guarantees. (Solr4.0+)

A soft commit is much faster since it only makes index changes visible and does not fsync index files or write a new index descriptor. If the JVM crashes or there is a loss of power, changes that occurred after the last hard commit will be lost. Search collections that have near-real-time requirements (that want index changes to be quickly visible to searches) will want to soft commit often but hard commit less frequently.

waitSearcher

block until a new searcher is opened and registered as the main query searcher, making the changes visible.

expungeDeletes

Merge segments with deletes away. (Solr1.4+)