尝试访问数组时尝试获取非对象的属性

Question

I'm trying to access a array via its index, but I need to get this from the query string.

I've tried:

 $var = $_GET['id'];
 echo $xml->subway->line[$var]->name;

That doesn't work. But this does:

 echo $xml->subway->line[0]->name;

Answer 1

try this:

$var = isset($_GET['id']) ? (int)$_GET['id'] : false;

if ($var !== false && isset($xml->subway->line[$var]) {
   echo $xml->subway->line[$var]->name;
} else {
   echo 'Your problem is either "id" not being in $_GET or $xml object does not have line with that index';

   var_dump($_GET); //see what is 'id'
}

Everytime you are getting item from an array by index you should check if it is set first to avoid errors like this.

Answer 2

It's likely that your $_GET variable is coming back as a string instead of an integer so PHP will be assuming the index doesn't exist. Try type casting it as

$var = (int)$_GET['id'];

Which forces PHP to treat the $_GET as an integer