- microtime: documentation ( source)
- explode: documentation ( source)
- date: documentation ( source)
- sprintf: documentation ( source)
<?php
for($i = 0; $i < 1000; $i++) {
list($s1, $s2) = explode(' ', microtime());
date('YmdHis').(float)sprintf('%.0f', (floatval($s1) + floatval($s2)) * 1000);
}