$id_conn mysql_connect( [...] ) or return [...]
this generate a parse error "unexpected T_RETURN"
there is an elegant method to do this without errors? 😉
return()s must be in an if () iteration if you wish to use them. You cannot use the statement ? true : false format or the format you are using.
Try:
<?php if ($id_conn = mysql_connect( [...] )) { // code } else { return [...] } ?>