var sheet = SpreadsheetApp.getActive().getSheetByName('YourSheetNameHere')
<?php
$sheets = array();
// ... load library and set up client ...
$service = new Google_Service_Sheets($client);
$response = $service->spreadsheets->get($spreadsheetId);
foreach($response->getSheets() as $s) {
$sheets[] = $s['properties']['title'];
}
return $sheets;
?>