Get all the nodes in the system
The easiest way would be to use entity_load()

$nodes = entity_load('node');


If you don't provide the second argument ($ids) it will load up all entities of the given type:


  $ids: An array of entity IDs, or FALSE to load all entities.


Just for the sake of completeness node_load_multiple() doesn't require the $conditions parameter so you could also grab all of the node ids from the database

$nids = db_query('SELECT nid FROM {node}')-&gt;fetchCol();


And then use $nids to load the nodes:

$nodes = node_load_multiple($nids);