Apache modules not available for subdomains

I've got a strange problem. I've installed some modules -- like memcached. If I run get_loaded_extensions() I can see that many more are loaded on a primary domain than on a subdomain. How do I get all of the modules available to the subdomain? From the primary domain of the account: [QUOTE][0] => Core [1] => date [2] => ereg [3] => libxml [4] => openssl [5] => pcre [6] => sqlite3 [7] => zlib [8] => bcmath [9] => calendar [10] => ctype [11] => curl [12] => dom [13] => hash [14] => filter [15] => ftp [16] => gd [17] => gettext [18] => SPL [19] => session [20] => json [21] => mbstring [22] => mcrypt [23] => standard [24] => mysql [25] => mysqli [26] => mysqlnd [27] => Phar [28] => posix [29] => Reflection [30] => imap [31] => SimpleXML [32] => sockets [33] => exif [34] => tokenizer [35] => xml [36] => xmlreader [37] => xmlwriter [38] => zip [39] => cgi-fcgi [40] => PDO [41] => pdo_sqlite [42] => imagick [43] => memcache [44] => memcached [45] => pdo_mysql [46] => ionCube Loader [47] => Zend Guard Loader
From a subdomain on the same account: [QUOTE] [0] => Core [1] => date [2] => ereg [3] => libxml [4] => openssl [5] => pcre [6] => sqlite3 [7] => zlib [8] => bcmath [9] => calendar [10] => ctype [11] => curl [12] => dom [13] => hash [14] => filter [15] => ftp [16] => gd [17] => gettext [18] => SPL [19] => session [20] => json [21] => mbstring [22] => mcrypt [23] => standard [24] => mysql [25] => mysqli [26] => mysqlnd [27] => Phar [28] => posix [29] => Reflection [30] => imap [31] => SimpleXML [32] => sockets [33] => exif [34] => tokenizer [35] => xml [36] => xmlreader [37] => xmlwriter [38] => zip [39] => cgi-fcgi
Thanks for any tips or thoughts! I've been spending HOURS trying to figure this out. :(