Pass variables to drupal template - drupal

Question

I need to display a page in drupal that is created by a template and based on a specific record from my table.
I created the module "item" (as an example).
I made the item_menu hook:
$items['items/%item'] = array(
'title' => 'Items',
'page callback' => 'drupal_get_form',
'page arguments' => array('show_item', 1),
'access callback' => true,
'access arguments' => array(),
);
I created a load function for the item:
function item_load($itemid)
{
$sql = 'SELECT * FROM {items} it WHERE it.id = :itemid';
$result = db_query(
$sql,
array(':itemid' => $itemid),
array( 'target' => 'mydatabase' ));
$item = $result->fetchObject();
return $item;
}
Now I want to use a template to display the specifics for the item, so I made a item module
a item.tpl.php. and a item_theme hook to register the template:
function item_theme($existing, $type, $theme, $path)
{
return array(
'show_item' => array(
'template' => 'item',
'variables' => array(),
),
);
}
The final thing I need to do is pass the item object to the item.tpl.php so I can display the item properties.
But I don't know how to do this. How can I make the item known within the template??
I hope the question is clear enough. Thanks in advance.
[edit]
I found that arg(1) contains the value of the wildcard from the menu page arguments, should I use arg(1) to look up the item in the database?

Answer 1

You need to declare the names and default values for the vars you want to use in the variables part of your array in hook_theme:
function item_theme($existing, $type, $theme, $path) {
return array(
'show_item' => array(
'template' => 'item',
'variables' => array('var1' => NULL, 'var2' => NULL, 'etc...'),
),
);
}
Then call the theme function like this:
$item_output = theme('show_item', array('var1' => $a_var, 'var2' => $another_var));
** UPDATE **
To address the load() function being called 4 times you can use static vars to avoid the query being run every time:
function item_load($itemid) {
$items = &drupal_static(__FUNCTION__, array());
if (!isset($items[$itemid])) {
$sql = 'SELECT * FROM {items} it WHERE it.id = :itemid';
$items[$itemid] = db_query(
$sql,
array(':itemid' => $itemid),
array('target' => 'mydatabase')
)->fetchObject();
}
return $items[$itemid];
}