警告:in_array()期望参数2为数组，给定null [英] Warning: in_array() expects parameter 2 to be array, null given

问题描述

尝试向会话中添加数据(并检查其是否已存在)时，我收到以下警告.

I am getting the following warning when trying to add data to a session (and checking if it already exists).

警告:in_array()期望参数2为数组，给定为空

Warning: in_array() expects parameter 2 to be array, null given

我该如何解决?

它所指的代码:

if(isset($_GET['product']) && !in_array($_GET['product'], $_SESSION['product'])){
    $_SESSION['product'][] = $_GET['product'];
}

只有在已清洁的浏览器中添加第一个产品时，我才会收到此警告.当我删除它并添加其他产品时，警告消失了.如果添加第二个产品，则相同.

I only get this warning when adding the first product on a cleaned browser. When I remove it and add another product the warning is gone. Same if I add a second product.

推荐答案

警告说明了一切.此参数为空:

The warining says it all. This param is null:

 $_SESSION['product']

使用前请确保已设置.示例:

Make sure it is set before you use it. Example:

if(isset($_SESSION['product']) && isset($_GET['product']) &&  !in_array($_GET['product'], $_SESSION['product'])){
        $_SESSION['product'][] = $_GET['product'];
    }

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