A richer option for PHP integration is the solr-php-client. It is available at http://code.google.com/p/solr-php-client/. Interestingly enough, this project leverages the JSON writer type to communicate with Solr instead of the PHP writer type, showing the prevalence of JSON for facilitating interapplication communication in a language-agnostic manner. The developers chose JSON over XML because they found that JSON parsed much quicker than XML in most PHP environments. Moreover, using the native PHP format requires using the eval() function, which has a performance penalty and opens the door for code injection attacks.

The solr-php-client can both create documents in Solr as well as perform queries for data. In /examples/9/solr-php-client/demo.php, there is a demo on how to create a new artist document in Solr for the singer Susan Boyle, and then performing some queries. Installing the demo in your specific local environment is left as an exercise for the reader. On a Macintosh, you should place the solr-php-client directory in /Library/WebServer/Documents/.

An array data structure of key value pairs that match your schema can be easily created and then used to create an array of Apache_Solr_Document objects to be sent to Solr. Notice that we are using the artist ID value -1. Solr doesn't care what the ID field contains, just that it needs to be present. Using -1 ensures that we can find Susan Boyle by ID later!

 $artists = array(
  'susan_boyle' => array(
   'id' => 'Artist:-1',
   'type' => 'Artist',
   'a_name' => 'Susan Boyle',
   'a_type' => 'person',
   'a_member_name' => array('Susan Boyle')
  )
 );

The value for a_member_name is an array, because a_member_name is a multivalued field.

Sending the documents to Solr and triggering the commit and optimize operations is as simple as follows:

  $solr->addDocuments( $documents );
  $solr->commit();
  $solr->optimize();

If you are not running Solr on the default port, then you will need to tweak the Apache_Solr_Service configuration:

$solr = new Apache_Solr_Service( 'localhost', '8983', '/solr/mbartists' );

Queries can be issued using one line of code; the variables $query, $offset, and $limit contain what you would expect them to:

$response = $solr->search( $query, $offset, $limit );

Displaying the results is very straightforward as well. Here we are looking for Susan Boyle based on her ID of -1, highlighting the result using a blue font:

foreach ( $response->response->docs as $doc ) { 

  $output = "$doc->a_name ($doc->id) <br />";

  // highlight Susan Boyle if we find her.
  if ($doc->id == 'Artist:-1') {
    $output = "<em><font color=blue>" . $output . "</font></em>";
   }

  echo $output;
}

Successfully running the demo creates Susan Boyle and issues a number of queries. Notice that if you know the ID of the artist, it's almost like using Solr as a relational database to select a single specific row of data. Instead of select * from artist where id=-1, we did q=id:"Artist:-1", but the result is the same!

Drupal is a very successful open source Content Management System (CMS) that has been used for building everything from the WhiteHouse.gov site to political campaigns and university websites. Drupal's built-in search has always been considered adequate, but not great, so the option of using Solr to power search is very popular.