compare and convert format for two different date

<?php

function convertDateRange($s,$f) {
    $time_s = strtotime($s);
    $time_f = strtotime($f);
    
    if(date("Y",$time_s) <> date("Y",$time_f)) {
        $date = date("j F Y",$time_s)."-".date("j F Y",$time_f);
    } else {
        if(date("m",$time_s) <> date("m",$time_f)) {
            $date = date("j F",$time_s)."-".date("j F Y ",$time_f);
        } else {
            if(date("d",$time_s) <> date("d",$time_f)) {
                $date = date("j",$time_s)."-".date("j F Y",$time_f);
            } else {
                $date = date("j F Y",$time_f);
                }
            }
        }
    return switchDate($date);
} // <end> convertDateRange

?>

this script compare two date and merge year, month, day based.
eg: start_date: 2011-11-15 00:00, end_date: 2011-12-5 00:00
result: 15 November - 5 December 2011

Usage

print convertDateRange('2011-11-15 00:00','2011-12-05 00:00');