Undefined variable: query - codeigniter - codeigniter

Question

I am getting the message:
A PHP Error was encountered
Severity: Notice
Message: Undefined variable: query
Filename: views/main.php
Line Number: 12
This is the code for my controller:
function get_all(){
$this->load->model('book_model');
$this->load->library('table');
$this->load->helper('html');
$data['query'] = $this->books_model->books_getall();
$this->load->view('main', $data);
}
And this is my view:
<h1> List of books in library</h1>
<table border="1"/>
<tr>
<th>ID</th>
<th>Title</th>
<th>Author</th>
<th>Information</th>
<th>Publisher</th>
<th colspan="2">Action</th>
</tr>
<?php
if(is_array($query)){
foreach ($query as $row){
echo "<tr>";
echo "<td>".$row->id."</td>";
echo "<td>".$row->title."</td>";
echo "<td>".$row->author."</td>";
echo "<td>".$row->information."</td>";
echo "<td>".$row->publisher."</td>";
echo "<td>".anchor('book/input'.$row->id,'Edit')."</td>";
echo "<td>".anchor('book/delete'.$row->id,'Delete')."</td>";
echo "</tr>";
}
}
?>
</table>
Thanks in advance for any help
Edit: This is my model code:
function get_all(){
$this->load->database();
$query = $this->db->get('books');
return $query->result();
}

Answer 1

From what I can see, line 12 appears to be this line:
if(is_array($query)){
And the error message is saying that $query is undefined. When you pass $data['query'] through to the view, that becomes $query.
I note your model is also returning $query->result(). This is not correct - result() should be used inside a loop to loop through the results, and you can use num_rows() to test for more than zero results, as in this example:
Model
function example()
{
$query = $this->db->get('books');
return $query;
}
Controller
$this->load->model('book_model');
$this->load->library('table');
$this->load->helper('html');
$data['query'] = $this->books_model->books_getall();
$this->load->view('main', $data);
View
if($query->num_rows() > 0)
{
foreach($query->result() as $row)
{
// Do stuff here on each $row
}
}
I suggest you take a look at this part of CodeIgniter's documentation, which is actually very good.