parse_url() is a great function, but a counterpart to it would be even better.

Can we have a create_url() or create_query_string() function which would take an array of items and build it using the local value of arg_separator ?  A lot of users do NOT use arg_separator because many programs are written with & as the separator (and there is little documentation about it).  Programmers should want to accomodate ALL users though and support those which use ";" or "|" as the separator when writing programs designed to display URLs to get from page to page of their application.

$base = "/search.php";
$qs = array ("action" => "search", "word" => "php");
echo create_url($base, $qs);

If the arg_separator is set to ";" the above script would output:  /search.php?action=search;word=php

Also, ini_get("arg_separator") and get_cfg_var("arg_separator") don't work if it was set in .htaccess.  Could we perchance also have get_master_cfg_value() and get_local_cfg_value()?  Those would help solve the problem above, though programmers would have to write their own create_url() function to build urls with the arg_separator value. 

All three of those should be supported by PHP natively IMHO.