_trip_search_excerpt_replace uses array_walk incorrectly

array_walk passes in a reference to the callback, so you should be modifying the value in place instead of returning the value. Also, since you're going to be using the quoted value in a regex that uses / as the delimiter, use that as the delimiter argument to preg_quote().

This fixes the problem that searching for "foo/car" gives a PHP warning: "warning: preg_replace(): Unknown modifier 'c' in trip_searh.module on one 654"

Line numbers may be off, we've got a patched version of the module, but line 654 for me is:
$text = preg_replace('/('. implode('|', $keys) .')/i', '\0', $text);

===================================================================
--- trip_search.module (revision 433)
+++ trip_search.module (working copy)
@@ -658,8 +658,8 @@
/**
* Helper function for array_walk in trip_search_excerpt.
*/
-function _trip_search_excerpt_replace($text) {
- return preg_quote($text);
+function _trip_search_excerpt_replace(&$text) {
+ $text = preg_quote($text, "/");
}