Get current WP sidebar

functions.php

<?php

if ( ! function_exists( 'get_current_sidebar' ) )
{
	function get_current_sidebar ( $widget_id )
	{
		$sidebars_widgets = get_option('sidebars_widgets', array());
		if ( is_array( $sidebars_widgets ) && isset( $sidebars_widgets['array_version'] ) )
			unset( $sidebars_widgets['array_version'] );
	
		$active_sidebars = apply_filters( 'sidebars_widgets', $sidebars_widgets );
	 
		foreach ( $active_sidebars as $sidebar => $widgets )
			if ( count( $widgets ) >= 1 )
				if ( false !== array_search( $widget_id, $widgets ) && NULL !== array_search( $widget_id, $widgets ) )
				return $sidebar;
		
		return false;
	}
}

widget.php

<?php

// inside your Widget Class
function widget ( $args, $instance )
{
	...
	
	// get the current sidebar's ID as used when registered, ie sidebar-default
	$current_sidebar = get_current_sidebar( $this->id );
	
	// you could use the output in a switch, just using some dummy sidebar names here
	switch ( $sidebar )
	{
		case 'sidebar-blog':
			$widget_content = 'test';
		break;
		
		case 'main-footer':
			$widget_content = 'Other content';
		break;
			
		default:
			$widget_content = '<b>Default</b>';
		break;
	}
	
	...
}