Suggestions for optimization?

From: Galen (phplist_at_zinkconsulting.com)
Date: 11/29/03 

To: php-general@lists.php.net
Date: Sat, 29 Nov 2003 09:32:19 -0800

I'm working on some database search ranking code. It currently
represents 95-98% of the time spent when doing fuzzy seaches. I have
tried my best to optimize my code - algorithmic shortcuts, eliminating
session variables, unsetting irrelevant results, etc and benchmarking
to find the best techniques. That's given me over a 10x improvement.
Unfortunately, because of the number of results it must process (up to
20,000), it is still somewhat slow. I think it could use some code
structure/formating tweaks to eek out that last bit of performance, but
I don't know much about optimizing PHP code in that way. Does anybody
have suggestions?

Also, might there be some tweaks for PHP itself to improve performance?
I already know about the Zend Optimizer and have it installed, it does
help.

Thanks!

Here's my code:

        if ($search_results[0]["relevancy"] == "")
        {
                function cmp($a, $b)
                {
                        if($a["relevancy"] < $b["relevancy"])
                        {
                                return 1;
                        }
                        elseif($a["relevancy"] > $b["relevancy"])
                        {
                                return -1;
                        }
                        else
                        {
                                return 0;
                        }
                }
                
                $search_statements = $_SESSION["search"]["statements"];
                
                foreach($search_results as $key1 => $value1)
                {
                        $num_fields_matched = 0;
                        $result_score = 0;
                        $metaphone_ratio = 0;
                        foreach($search_statements as $key => $value)
                        {
                                if ($value != "" AND $value1[$key] != $value)
                                {
                                        $value = strtolower(trim($value));
                                        $value1[$key] = strtolower(trim(($value1[$key])));
                                        $num_fields_matched++;
                                        $value_metaphone = metaphone($value1[$key]);
                                        $search_metaphone = metaphone($value);
                                        $search_position = strpos($value1[$key], $value);
                                        $string_count = substr_count($value1[$key], $value);
                                        $levenshtein = levenshtein($value, $value1[$key], "0.5", 1, 1);
                                        
                                        if ($search_metaphone == $value_metaphone AND $value_metaphone !=
"")
                                        {
                                                $metaphone_ratio = 1;
                                        }
                                        elseif ($search_metaphone != 0)
                                        {
                                                $metaphone_ratio = 0.6 * (1 / levenshtein($search_metaphone,
$value_metaphone));
                                        }
                                        
                                        $result_score = $result_score + ($levenshtein + (8 *
$search_position)) - (2 * ($string_count - 1)) - (1.1 *
$metaphone_ratio * $levenshtein);
                                }
                                elseif ($value1[$key] == $value)
                                {
                                        $result_score = $result_score - 5;
                                }
                        }
                        if ($num_fields_matched == 0)
                        {
                                $num_fields_matched = 1;
                        }
                        $search_results[$key1]["relevancy"] = ($result_score * -1) /
$num_fields_matched;
                        
                        if ($fuzzy_search == true AND $search_results[$key1]["relevancy"] <
-5)
                        {
                                unset($search_results[$key1]);
                        }
                }
                
                usort($search_results, "cmp");
        }