Indexing library for PHP/MySQL

create.sql

CREATE TABLE `data_index` (
  `id` int(11) NOT NULL,
  `num` smallint(6) NOT NULL,
  `word` varchar(33) DEFAULT NULL,
  PRIMARY KEY (`id`,`num`),

  KEY `word` (`word`,`id`),

  KEY `id` (`id`,`word`)
);

index-demo.php

<?
require_once "lib_ix.php";

mysql_connect('localhost', 'root', 'pass');
mysql_select_db('database');


mysqlix_index("data", "id", "`desc`", "data_index");

lib_ix.php

<?

function mysqlix_create($ixtable){
        return "
                create table `$ixtable`(
                        id      int not null            ,
                        num     smallint not null       ,
                        word    varchar(33)             ,

                        primary key(id, num)            ,
                        index(word, id)                 ,
                        index(id, word)
                )
        ";
}

function mysqlix_value_format($v){
        $v = preg_replace('/[^0-9A-Za-z]/', ' ', $v);
        $v = strtolower($v);
        $vals = explode(" ", $v);

        $vv = array();
        foreach($vals as $v){
                $v = trim($v);
                if ($v == "")
                        continue;

                $vv[] = mysql_real_escape_string(md5($v));
        }

        return $vv;
}

function mysqlix_hot_index($k, $v, $ixtable){
        $vals = mysqlix_value_format($v);

        //print_r($vals);

        mysql_query( "DELETE FROM `$ixtable` WHERE id = $k" );

        $no = 0;
        foreach($vals as $v){
                mysql_query( "REPLACE INTO `$ixtable` VALUES( $k, $no, '$v' )" );
                $no++;
        }
}

function mysqlix_index($table, $key, $value, $ixtable=""){
        if ($ixtable == "")
                $ixtable = $table . "_index";

        if ($value == "")
                return;

        $sql = "SELECT `$key` as k, $value as v FROM `$table` ";

        mysqlix_index_sql($sql, $ixtable);
}

function mysqlix_index_sql($sql, $ixtable){
        $result = mysql_query( $sql );

        while ($row = mysql_fetch_array($result)) {
                echo sprintf("%8s | %-100s \n", $row[0], $row[1]);

                mysqlix_hot_index($row[0], $row[1], $ixtable);
        }
}

function mysqlix_search($value, $ixtable, $limit=100){
        $v = mysqlix_value_format($value);

        if (count($v) == 0)
                return array();

        $DISTINCT = count($v) > 1 ? "DISTINCT" : "";

        $sql = "
                        SELECT $DISTINCT
                                t0.id as id
                        FROM
        ";

        for( $i = 0; $i < count($v); $i++){
                $sql = $sql . "
                                `$ixtable` t$i ";

                if ( $i < count($v) -1 )
                        $sql = $sql . ",";

                $sql = $sql . "\n";
        }

        $sql = $sql . "
                        WHERE
        ";

        for( $i = 0; $i < count($v); $i++){
                $val = $v[$i];

                $sql = $sql . "
                                t$i.word = '$val'       AND
                ";
        }

        if (count($v) > 1){
                for( $i = 0 + 1; $i < count($v); $i++){
                        $sql = $sql . "
                                t0.id = t$i.id          AND
                        ";
                }
        }

        $sql = $sql . "
                                1 = 1
                        LIMIT
                                $limit
        ";


        echo $sql;

        $result = mysql_query($sql);

        $x = array();

        while ($row = mysql_fetch_array($result))
                $x[] = $row['id'];

        return array_unique($x);
}

search-demo.php

<?
require_once "lib_ix.php";

mysql_connect('localhost', 'root', 'pass');
mysql_select_db('database');


$x = mysqlix_search($argv[1], "data_index");

print_r($x);

However, performance is poor if there are lots of data.
I tried with ~7M (index is ~28M) and if you search by 2-3 words, result comes in 4-5 sec.

Possible fix could be dropping "num" column and making only one primary on "word" + "id", but performance is still poor.