- var_dump: documentation ( source)
<?php
$dateTime = new DateTime();
//Format: customer_export_2013-07-30_173612.csv
$_filePrefix = 'customer_export_';
$_timestamp = $dateTime->format('Y-m-d_His');
$_hundreths = ($dateTime->format('u') / 1000);
var_dump($_hundreths);