(PECL mongo >=0.9.0)
MongoGridFS::findOne — Returns a single file matching the criteria
$query = array()
   [, mixed $fields = array()
  ]] )
query
     The filename or criteria for which to search.
   Returns a MongoGridFSFile or NULL.
  
Example #1 MongoGridFS::findOne() example
Example demonstrating how to find a single file from the MongoGridFS.
<?php
$downloads = $mongo->my_db->getGridFS('downloads');
$downloads->storeFile('filename.tgz');
$download = $downloads->findOne('filename.tgz'); // instance of MongoGridFSFile
print_r($download);
?>
See MongoGridFSFile for more information about how to work with files.
The above example will output something similar to:
MongoGridFSFile Object
(
    [file] => Array
        (
            [_id] => MongoId Object
                (
                )
            [filename] => filename.tgz
            [uploadDate] => MongoDate Object
                (
                    [sec] => 1274288014
                    [usec] => 467000
                )
            [chunkSize] => 262144
            [md5] => d41d8cd98f00b204e9800998ecf8427e
        )
    [gridfs:protected] => MongoGridFS Object
        (
            [chunks] => MongoCollection Object
                (
                )
            [filesName:protected] => downloads.files
            [chunksName:protected] => downloads.chunks
        )
)