[PHP-DB] global vars

[olinux]

I am working with global variables and functions, specifically calling a function 
inside another function.
I checked the online docs and don't see any problems with what i have... i declare the 
table_name as global inall functions

What I am trying to do is DELETE all entries for a uid before INSERTING the new skills
my insert_skills() calls the function to DELETE entries and then the function that 
creates the INSERT query

the lookup_skills table columns looks like this.
   |   id   |   uid   |   skills_id   |


here are a couple excerpts from my code:

table_name = "lookup_skills";
...

function insert_skills($uid, $skills) {
global $table_name;
   purge_lookup($table_name, "1");

   $query = create_checkbox_query($skills, $table_name, "1");

...

function purge_lookup($table, $uid) {
global $table_name;
  $q = "DELETE FROM $table, WHERE uid = $uid";
  mysql_query($q);
}

...

function create_checkbox_query($arr, $table, $uid) {
global $table_name;
   $q = "INSERT INTO $table (uid, skill_id) VALUES";
   foreach ($arr as $check) {
     $q .=  " ( $uid , $check )" . ",";
   }
   return substr($q, 0, -1);
}

insert_skills("1", $skills);

thanks much,
olinux