How to write a custom php code in joomla

I am working on a joomla website but as I am new to joomla so I dont know exactly how to write a data uploading form for an administrator.Actually I want to make a form for administrator through which he will be uploading information about p开发者_JAVA百科roperties ,few pictures and some other information in the form of textfields , comboboxes and radio buttons.Once the data uploads then user will be able to search these properties by providing some information (in the form of textfields,comboboxes etc ).I know how to do these things in other own written websites but don't know how to do it in joomla.As far as I know there are a lot of extensions but they are very costly thats why I want to do it myself

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'very costly' is a very subjective term. I've rarely seen a Joomla add-on cost more than £30 or £50 (approx $50 - $80). Some add-ons are more perhaps double this - but they tend to be full apps that will just drop in and run a full business.

http://docs.joomla.org/ and in particular this page: http://docs.joomla.org/Component_Development should be your starting points.

As you are just starting out you probably want to follow the Joomla 1.7 items where possible. Where not possible Joomla 1.6 is almost identical internally.

Browse the code of the 'core' components that ship with Joomla - within the /components/ and /administrator/components/ folders. Download extensions from the JED (Joomla Extensions Directory) http://extensions.joomla.org/ and pick those apart too.

Andrew Eddie - Joomla's former lead developer - offers video tutorials for a very minor subscription fee at his site http://learn.theartofjoomla.com/