undefined offset 0

i got my theme installed with some trial and error, but on activating required plugins, got this message:

Notice: Undefined offset: 0 in /home/choonzqr/public_html/wp-includes/plugin.php on line 898

Notice: Undefined offset: 0 in /home/choonzqr/public_html/wp-includes/plugin.php on line 916

Warning: Cannot modify header information – headers already sent by (output started at /home/choonzqr/public_html/wp-includes/plugin.php:898) in /home/choonzqr/public_html/wp-includes/pluggable.php on line 1173

Warning: Cannot modify header information – headers already sent by (output started at /home/choonzqr/public_html/wp-includes/plugin.php:898) in /home/choonzqr/public_html/wp-includes/pluggable.php on line 1173

nothing else shows anywhere now. no idea what to do with this code!!
i decided to ftp to look at the code, but i don’t know how to fix it.
this is lines 898 to 916…

if (is_object($function[0]) ) {
		// Object Class Calling
		if ( function_exists('spl_object_hash') ) {
			return spl_object_hash($function[0]) . $function[1];
		} else {
			$obj_idx = get_class($function[0]).$function[1];
			if ( !isset($function[0]->wp_filter_id) ) {
				if ( false === $priority )
					return false;
				$obj_idx .= isset($wp_filter[$tag][$priority]) ? count((array)$wp_filter[$tag][$priority]) : $filter_id_count;
				$function[0]->wp_filter_id = $filter_id_count;
				++$filter_id_count;
			} else {
				$obj_idx .= $function[0]->wp_filter_id;
			}

			return $obj_idx;
		}
	} else if ( is_string($function[0]) ) {

can anyone help me make sense of this please? i don’t know php (and am only just learning wordpress…the hard way!).