if you want to redeclare a PHP-function
using i.e.
function pg_query($args){
...
}
you'll get an error (of course).
To redeclare existing functions the following works:
define(pg_query, pg_query_user);
function pg_query_user($args){
print "pg_query was used";
}
pg_query("foo");
output: pg_query was used