PHP -添加1天到日期格式的mm-dd-yyy。

<?php
    $date = "04-15-2013";
    $date = strtotime($date);
    $date = strtotime("+1 day", $date);
    echo date('m-d-Y', $date);
?>
<?php
    $date = "04-15-2013";
    $date = str