WordPress at a glance
filter is not described

posts_search filter-hook . WP 3.0.0

Filters the search SQL that is used in the WHERE clause of WP_Query.

Usage

add_filter( 'posts_search', 'filter_function_name_8988', 10, 2 );
function filter_function_name_8988( $search, $this ){
	// filter...

	return $search;
}
$search(string)
Search SQL for WHERE clause.
$this(WP_Query)
The current WP_Query object.

Where the hook is called

WP_Query::get_posts()
wp-includes/class-wp-query.php 1956
$search = apply_filters_ref_array( 'posts_search', array( $search, &$this ) );

Where the hook is used (in WP core)

Does not used.