在while循环中有日期比较的奇怪行为 [英] Strange behaviour in a while loop with a date compare in PHP

问题描述

我正在尝试创建一个简单的while循环，该循环从PHP中的数据库中提取一个关联数组。本质上，我想对从数据库中提取的日期与当前日期进行比较。这里是要抓住的地方。不同部分（表中表示）有不同的截止日期。因此，我需要通过减去某些天数来修改从数据库中提取日期的日期。我用不同的变量完成了此操作，但得到了一些奇怪的结果，这些结果与我指定的结果不同。我想念什么吗？

Hi I am trying to create a simple while loop that pulls an associative array from a database in PHP. In essence I want to then do a compare on the date pulled from the database with the current date. Here is the catch. Different sections (represented in a table) have different deadlines. So I need to modify the pulled date from the database by subtracting certain amounts of days. I have done this with different variables but I get some weird results which are not the ones I have specified. Am i missing something?

$today = date("Y-m-d") 

while ($query_row = sqlsrv_fetch_array($stmt, SQLSRV_FETCH_ASSOC))

                    {          

    $date =  $query_row['DueDate'];// this is the due date from the  server
    $duedate = $date->format('d-m-Y'); // to output in table
    $compare1 = $date;
    $compare2 = $date;
    $compare3 = $date;
    $compare4 = $date;                             
    $compare1->modify('-4 days');
    $compare2->modify('-3 days');
    $compare3->modify('-2 days');
    $compare4->modify('-1 day');


    echo $today.' today <br/>';
    //just for debugging
    echo $date ->format('Y-m-d').' due date <br/>';
    echo $compare1->format('Y-m-d').' minus 4 date <br/>';

    if (  $today >= $compare1 )
    {   

        $Triginsert = 'style="background-color: #ff0000;"';

    }
    else 
    {

        $Triginsert = '';
    }
    }

您可以看到当前日期是否大于或等于比较日期，该日期应该是从服务器提取的日期-4天，然后应将其变为红色，否则它什么都不做。。

As you can see if the current date is greater than or equal to the compared date which should be the date pulled from server - 4 days then it should turn the block red else it should do nothing..

任何帮助都会大。

谢谢

推荐答案

发生的事情是，由于对象是由在php 5+中引用，您所有的$ compare变量都是对同一原始$ date对象的引用。因此，您要反复修改同一个而不是创建4个单独的对象。参见 http://www.php.net/manual/en/language。 oop5.references.php 。
您想要的是：

what's happening is that since objects are assigned by reference in php 5+, all your $compare variables are references to the same original $date object. So you are modifying the same one repeatedly instead of creating 4 separate ones. See http://www.php.net/manual/en/language.oop5.references.php . What you want instead is:

$compare1 = clone $date;
$compare2 = clone $date;
etc.

BTW当您使用var_dump（$ query_row ['DueDate' ]）？我以为它已经是一个日期对象，否则-> modify（）调用将立即出错，并且您说的是您得到的是怪异的行为，而不是错误消息，但是其他一些答案都假定$ query_row [' DueDate']是一个字符串，因此我想再次检查。

BTW what do you get when you var_dump($query_row['DueDate']) ? I was assuming it was already a date object, otherwise the ->modify() calls would error immediately, and you were saying you were getting weird behavior rather than an error message, but some of the other answers are assuming that $query_row['DueDate'] is a string so I wanted to double check.

这篇关于在while循环中有日期比较的奇怪行为的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！