this script displays the list of suppliers & orders like
$supplier given on input arg.
this page brings differents features like to display supplier's details,
to add an order for a specific supplier or to just add a new supplier.
$supplier is the suplier we have to search order.
OP can be equals to 'close' if we have to close a basket before building the page.
basket we have to close if op is equal to 'close'.