本月php的循环日期

Question

提供下面的代码，输出是（见下文）。我的问题是为什么在2009/11/01之后，在2009/11/30和2009/12/30之前，而不是2009/12/01。从2009/06/01〜2009/11/01没有问题。

输出
2009/06/01
2009/07/01
2009/08/01
2009/09/01
2009/10/01
2009/11/01
2009 /30分之11
2009/12/30

我的代码

<?php 

$startdate = "2009/06/01"; 
$enddate = "2009/12/31"; 

$start = strtotime($startdate); 
$end = strtotime($enddate); 

$currentdate = $start; 
while($currentdate < $end) 
{ 
    $cur_date = date('Y/m/d',$currentdate); 
    $month = date('m', $currentdate); 
    $year = date('Y', $currentdate); 
    $monthLength = daysOfMonth($month, $year); 
    $currentdate += $monthLength; 

    echo $cur_date . "<br />"; 
} 


function daysOfMonth($month, $year) 
{ 
    return (86400 * date("t", strtotime($year."-".$month."-01"))); 
} 

?> 

Answer 1

<?php 

$startdate = "2009/06/01"; 
$enddate = "2009/12/31"; 

$start = strtotime($startdate); 
$end = strtotime($enddate); 

$currentdate = $start; 
while($currentdate < $end) 
{ 
     $cur_date = date('Y/m/d', $currentdate); 

     $currentdate = strtotime('+1 month', $currentdate); 

     echo $cur_date . "<br />"; 
} 

?>