PHP 错误：“无法通过引用传递参数 2”
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/13105373/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
PHP error: "Cannot pass parameter 2 by reference"
提问by user1723760
I just need help on this PHP error which I do not quite understand:
我只需要关于这个我不太明白的 PHP 错误的帮助：
Fatal error: Cannot pass parameter 2 by reference in /web/stud/openup/inactivatesession.php on line 13
致命错误：无法在第 13 行的 /web/stud/openup/inactivatesession.php 中通过引用传递参数 2
<?php
error_reporting(E_ALL);
include('connect.php');
$createDate = mktime(0,0,0,09,05,date("Y"));
$selectedDate = date('d-m-Y', ($createDate));
$sql = "UPDATE Session SET Active = ? WHERE DATE_FORMAT(SessionDate,'%Y-%m-%d' ) <= ?";
$update = $mysqli->prepare($sql);
$update->bind_param("is", 0, $selectedDate); //LINE 13
$update->execute();
?>
What does this error mean? How can this error be fixed?
这个错误是什么意思？如何修复此错误？
回答by Gung Foo
The error means that the 2nd argument is expected to be a reference to a variable.
该错误意味着第二个参数应该是对变量的引用。
Since you are not handing a variablebut an integer of value 0, it generates said error.
由于您处理的不是变量，而是值为 0的整数，因此会产生上述错误。
To circumvent this do:
要避免这种情况，请执行以下操作：
$update->bind_param("is", $a = 0, $selectedDate); //LINE 13
In case you want to understand what is happening, as opposed to just fixing your Fatal error, read this: http://php.net/manual/en/language.references.pass.php
如果您想了解正在发生的事情，而不是仅仅修复您的Fatal error，请阅读：http: //php.net/manual/en/language.references.pass.php
回答by John Woo
First,you shouldn't use DATE_FORMATwhen you want to compare date because DATE_FORMATchanges it to string not date anymore,
首先，DATE_FORMAT当您想比较日期时不应使用，因为DATE_FORMAT将其更改为字符串而不是日期，
UPDATE Session
SET Active = ?
WHERE SessionDate <= ?
Second, store the value first on a variable and pass it on the paramater
其次，首先将值存储在变量上并将其传递给参数
$createDate = mktime(0,0,0,09,05,date("Y"));
$selectedDate = date('d-m-Y', ($createDate));
$active = 0;
$sql = "UPDATE Session SET Active = ? WHERE SessionDate <= ?";
$update = $mysqli->prepare($sql);
$update->bind_param("is", $active, $selectedDate);
$update->execute();
