注意：未定义的偏移量：使用if（）和elseif（）语句[关闭]在E：\ server \ htdocs \ file.php中为1

I am using this code:

<?php
include_once('/simple_html_dom.php');
$dom = file_get_html("http://www.gsmarena.com/samsung_i9300_galaxy_s_iii-4238.php");
foreach ($dom->find('tr') as $node) {
if (is_a($node->children(0), 'simple_html_dom_node')) {
    if ($node->children(0)->plaintext == "Protection") {
        $plain = explode(',', $node->children(1)->plaintext);
    if($plain[0] === null){echo 'Nu are';}
     elseif($plain[0]!== null) {echo $plain[0];
     if($plain[1] === null){echo 'Nu are';}
     elseif($plain[1] !== null) {echo $plain[1];} 
     }  
    }

    }
}

?>

All i want is if there exist $plain[x] or $plain[y] to shows me if not to display an custom text (in my case 'Nu are'). All is fine, code works good because $plain[1] not exist in present case, but I receive an error too.

Here is the result receved from code:

Corning Gorilla Glass 2 Notice: Undefined offset: 1 in E:\server\htdocs\preluare\1.php on line 10 Nu are

First is shows me offset 0, because exist and second offset not exist and shows me that error and after error is the correct custom text.

Correct result is Corning Gorilla Glass 2 Nu are

Instead of

$plain[1] !== null

use

array_key_exists(1, $plain)

or

isset($plain[1])