sorry for bumping this ancient post..
but this is exactly what i am looking for right now.. any idea ? :roll:

You can add &cat=2 as a search parameter and it will display results from the second category only.

So you can build a drop down menu with categories and set category ID as a value. You can use categories widget to build this menu.

There might be another way, let's wait for devs...

Open inc/widgets/widgets/_coll_search_form_widget.php and use this function to display the search form.
You still have to style categories select fieldset with css, I have no idea how to get rid of it.

function display( $params )
{
	global $Blog;

	$this->init_display( $params );

	// Collection search form:
	echo $this->disp_params['block_start'];

	$Form = & new Form( NULL, 'form' );
	$this->disp_title( T_('Search') );

	form_formstart( $Blog->gen_blogurl(), 'search', 'SearchForm' );
	
	echo '<br />';
	$s = get_param( 's' );
	echo '<input type="text" name="s" size="25" value="'.htmlspecialchars($s).'" class="SearchField" /><br />';
	
	// Category select
	$ChapterCache = & get_Cache( 'ChapterCache' );
	$Form->select_input_options( 'cat', $ChapterCache->recurse_select( NULL, $Blog->ID, true, NULL, 1 ), T_('Select category') );
	
	echo '<p>';
	$sentence = get_param( 'sentence' );
	echo '<input type="radio" name="sentence" value="AND" id="sentAND" '.( $sentence=='AND' ? 'checked="checked" ' : '' ).'/><label for="sentAND">'.T_('All Words').'</label><br />';
	echo '<input type="radio" name="sentence" value="OR" id="sentOR" '.( $sentence=='OR' ? 'checked="checked" ' : '' ).'/><label for="sentOR">'.T_('Some Word').'</label><br />';
	echo '<input type="radio" name="sentence" value="sentence" id="sentence" '.( $sentence=='sentence' ? 'checked="checked" ' : '' ).'/><label for="sentence">'.T_('Entire phrase').'</label>';
	echo '</p>';
	echo '<input type="submit" name="submit" class="submit" value="'.T_('Search').'" class="search_submit" />';
	echo '</form>';

	echo $this->disp_params['block_end'];

	return true;
}

thank you very much sam2kb, i am pretty sure it would work; but on second thought, that was not what i needed (:, i ve created a blog for each category, like 15 blogs for 15 categories, so ; what i need is a search form, among blogs not categories ..

This is much easier. Just create another blog, set it to aggregate all others and hardcode blog id in search widget.

sam2kb wrote:

This is much easier. Just create another blog, set it to aggregate all others and hardcode blog id in search widget.

actually i dont know if i am doing this right, but i am using Blog#1 for main blog to include all the other category-blogs, and am cross-posting in to Blog#1 using the other cat-blog's cats instead of aggregating..

so that i am able to actually include all posts under 1 blog instead of aggregating in order to be able to do different things, (for example, i did add a post_list widg. in the sidebar and made it 'random select' from 'blog1' and there you go 'a global random post widget for all blogs' (: )

i dont know if this is right, i hope crossposting as 2 wont hurt in future in perm urls etc..

thank you sam2kb, i guess as i already have blog1 to include all the other posts; i will just hardcode blog1 and will be able to search all content in a way..

i am just trying to figure out making an advanced search page lets say just for Blog#7 and blog#11 with being selected from checkboxes.. sounded hard to me but will try..cheers