未定义的索引:在C:wampwwwsearch1(2）.php中的第4行进行搜索

Undefined index: search in C:wampwwwsearch1 (2).php on line 4

$button = $_GET ['submit'];
$search = $_GET ['search']; 
if(!$button)
echo "you didn't submit a keyword!";
else

Undefined index: search in C:'wamp'www'search1 (2).php on line 4

在读取$_GET/$_POST/$_REQUEST中的数组键之前，请使用isset（）。

$button = isset($_GET['submit']) ? $_GET['submit'] : false;
$search = isset($_GET['search']) ? $_GET['search'] : false;
if(!$button) echo "you didn't submit a keyword!";