well, first of all to see if it is working,
if (!ini_set("session.use_trans_sid",0)) { print "ERROR SETTING USE_TRANS<hr>"; }
the PHP_INI_USER|PHP_INI_PERDIR just means you, php.ini, .htaccess, or httpd.conf can set this variable. you are able to set it, so it should work.
maybe it's a syntatical error, try
if (!ini_set("session.use_trans_sid","0")) { print "ERROR SETTING USE_TRANS<hr>"; }
or
if (!ini_set("session.use_trans_sid",NULL)) { print "ERROR SETTING USE_TRANS<hr>"; }