number from $_GET not being read into simplexml xpath query using php

THIS WORKS:

1 $number  = 2;
2 $allofit = simplexml_load_file("thexmlfile.xml");
3 $thebook = $allofit -> booklist[$number] -> abook;
4 echo $thebook;

THIS FOLLOWING DOES NOT WORK: But if I want to read $number from a from with method GET I set

 6 $number=$_GET[thenumber];   // $number=2 from the form//
 7 echo $number;              // and properly shows $number=2 --*/
 8 $allofit = simplexml_load_file("thexmlfile.xml");
 9 $thebook = $allofit -> booklist[$number] 开发者_运维百科-> abook;
 10 echo $thebook;

The echo on line 10 reports nothing (no error, just blank space in the html) even though I can successfully echo $number in line 7... so its being set, but just not picked up in line 9.. although the equivalent in line 3 works (!).

Any ideas folks?

Thanks in advance J

$number=$_GET[thenumber];

At this stage $number is a string.

Do you need to coerce it into an integer? Probably with intval? http://php.net/manual/en/function.intval.php

Try:

$number=intval($_GET[thenumber]); 

PHP should convert your "2" to a 2 without a problem. My guess is that you're missing quotes: $number=$_GET[thenumber]. Try $number=$_GET['thenumber'];