警告：in_array（）期望参数2为数组，给定为null

问题描述：

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

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

How can I fix this?

The code it is referring to:

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

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.

尝试向会话添加数据时（我检查它是否已存在），我收到以下警告。 / p>

警告：in_array（）期望参数2为数组，给定为空 p> blockquote>

我如何修复这个？ p>

它所指的代码： p>

  if（isset（$ _ GET ['product']）＆amp;＆amp;  ！in_array（$ _ GET ['product']，$ _SESSION ['product']））{
 $ _SESSION ['product'] [] = $ _GET ['product']; 
} 
  code>   pre> 
 
 我只在清理过的浏览器上添加第一个产品时收到此警告。 当我删除它并添加另一个产品时，警告消失了。 如果我添加第二个产品，则相同。 p> 
  div>

答

The warining says it all. This param is null:

 $_SESSION['product']

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'];
    }

答

Your $_SESSION['product'] is empty. Try this,

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

It should work.

答

check if the value is set before use it with isset and use is_array to check if a given variable is an array.

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

答

you should always apply check for array

isset( $_SESSION['product']) in your is condition before & condition

警告：in_array（）期望参数2为数组，给定为null

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