SolrClient is Working in browser, Not working in terminal Ubuntu 16.04

Question

I have following php script which is run perfectly in browser. But when I try to run in terminal, it throwing Fatal Error: Uncausght Error: 'SolrClient' not found for line($fetch_client = new SolrClient($fetch_options);)

$solr_ip = "192.168.0.5";
$solr_path   = '/solr/';
$solr_main_db = 'maindb';

$fetch_options = $insert_options = array (  'hostname' => $solr_ip,
                    'login'    => '',
                    'password' => '',
                    'port'     => '8983',
                    'path'     => $solr_path . $solr_main_db,
            ); 
$fetch_client = new SolrClient($fetch_options);

$query = new SolrQuery();

$query->setQuery('*:*');
$query->setStart(0);

$query->setRows(10);
$query->addSortField('id');    

$query_response = $fetch_client->query($query);

$response = $query_response->getResponse();
echo "<pre>";print_r($response);echo "</pre>";

What's wrong I am doing here? is there anything I am missing?

Note: I was running this script sometime ago with no issue. PHP version 7.0

Solr Version6.3

Ubuntu version 16.04

Your help is greatly appreciated!