In response to jharnett's question about accounts disabled by default from ldap_add, we have found a solution.
The attribute userAccountControl contains a value that includes whether the account is disabled or enabled. The default for us is 546; when we changed that to 544 the account became enabled. Changing whatever value is in userAccountControl by 2 seems to enable or disable the account.
The following code worked for us to create a new user with an enabled account:
$adduserAD["userAccountControl"] = "544";
We just added this element to the above example's array.
