(PECL solr >= 0.9.2)
SolrClient::request — Sends a raw update request
Sends a raw XML update request to the server
raw_requestAn XML string with the raw request to the server.
Returns a SolrUpdateResponse on success. Throws an exception on failure.
   Throws SolrIllegalArgumentException if raw_request was an empty string
  
Throws SolrClientException if the client had failed, or there was a connection issue.
Throws SolrServerException if the Solr Server had failed to satisfy the query.
Example #1 SolrClient::request() example
<?php
$options = array
(
    'hostname' => SOLR_SERVER_HOSTNAME,
    'login'    => SOLR_SERVER_USERNAME,
    'password' => SOLR_SERVER_PASSWORD,
    'port'     => SOLR_SERVER_PORT,
);
$client = new SolrClient($options);
$update_response = $client->request("<commit/>");
$response = $update_response->getResponse();
print_r($response);
?>
The above example will output something similar to:
...