print_r() not printing array

[AN-net]

for some reason when i use print_r() on this array it only prints array().
can someone explain to me why?

here is the code

PHP Code:

if($_REQUEST['do']=="index")
{
    $vbjclass= new vbjournal();
    
    $cache= $vbjclass->cache_journals();
    print_r ($cache);
    $journals= $vbjclass->grabjournals($cache);
}