Go easy on your use of commit - use the <autocommit /> section solrconfig.xml instead.
Also consider using optimize() once a day if you are doing lots of adds/removes.
(PECL solr >= 0.9.2)
SolrClient::commit — Finalizes all add/deletes made to the index
$maxSegments= "1" [, bool
$waitFlush= true [, bool
$waitSearcher= true ]]] )
This method finalizes all add/deletes made to the index.
Optimizes down to at most this number of segments. Since Solr 1.3
Block until index changes are flushed to disk.
Block until a new searcher is opened and registered as the main query searcher, making the changes visible.
Returns a SolrUpdateResponse object on success or throws a SolrClientException on failure.