Why is my first value in reset() null? - php

Question

I have a server with a directory full of books. I wrote a script which loops through this directory and lists out all the PDF's that are located inside. I then took it a step further and started searching Google books and bringing back the picture and description of these books. For some of the books this works perfectly, but for a good number of them I get this error...
Warning: reset() expects parameter 1 to be array, null given in bookDescriber.php on line 49
This the code that is giving this error (this is all inside a big foreach, which lists all the PDFs in the directory). the last line of this code is line 49.
//search GoogleBooks for a description
$item = file_get_contents("https://www.googleapis.com/books/v1/volumes?q=$v&maxResults=1");
$item = json_decode($item);
$item = reset($item->items);
the $v in the above url is simply the filename of the book, so this is one of the links it would generate and as you can see this does return information... (if you copy the entire link all the way to maxResults=1 then the data is returned, could it be that sometimes the spaces in the URL don't matter and sometimes they do?? I'm lost)
https://www.googleapis.com/books/v1/volumes?q=Ajax the definitive guide.pdf&maxResults=1
so why is the first parameter in my reset() set to null??? Help please!!

Answer 1

I've tested around with that snippet and it can be recreate if:
$v is blank
The book doesn't exist
If the book doesn't exist, the null error is thrown and Google returns:
{
"kind": "books#volumes",
"totalItems": 0
}
This isn't enough information to create an array. You are better off having a check like so:
<?php
$item = file_get_contents("https://www.googleapis.com/books/v1/volumes?q=$v&maxResults=1");
if(is_array($item))
{
$item = json_decode($item);
$item = reset($item->items);
}
else
{
return false; // echo 'no book';
}
?>