Shortcodes (with a space) added to php Sample

there isn’t an “space” in the Shortcode-Name. What you have, is an shortcode called “customcont”, that is providing an Parameter called “form”.

So this is, how it should work:

function example_shortcode( $atts = array(), $content="" )
{
    extract( 
        shortcode_atts( 
            array (
                'form' => 0,
            ), 
            $atts 
       )
   );

    return 'FORM TO DISPLAY IS #'.$form;
}
add_shortcode( 'customcont', 'example_shortcode' );

With the $form Variable you can Access the Number of the form to Display, in your case the “3”.