- date: documentation ( source)
- strtotime: documentation ( source)
<?php
$start= "2013-01-31";
$current = date('F', strtotime("first day of next month",strtotime($start)));
echo $current."\n";
$date = new DateTime('2013-01-31');
$date->modify( 'first day of next month' );
echo $date->format('F');