SQL filter on PHP results page (in custom Joomla module)

Avg Bid (AUD)
Project Budget (AUD)
$30 - $250

Project Description:
I need an SQL filter on PHP results page (in custom Joomla module) in the form of a dropdown box. It will show a list of all possible values of a certain field within the table as well as an "all" option, and the sql query is then to be filtered by the choice. Also, this filter must be able to be passed through the url (eg. [url removed, login to view]).
i need one filter done, i will then learn from your code and add more (needs to be able to support multiple filters)
Michael A.

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