Thoughts on Lucene, Solr, crawling and vertical search 

/**
* USAGE: mysql_safe( string $query [, array $params ] )
* $query - SQL query WITHOUT any user-entered parameters. Replace parameters with "?"
*     e.g. $query = "SELECT date from history WHERE login = ?"
* $params - array of parameters
*
* Example:
*    mysql_safe( "SELECT secret FROM db WHERE login = ?", array($login) );    # one parameter
*    mysql_safe( "SELECT secret FROM db WHERE login = ? AND password = ?", array($login, $password) );    # multiple parameters
* That will result safe query to MySQL with escaped $login and $password.
**/
function mysql_safe($query,$params=false) {
    if ($params) {
        foreach ($params as &$v) { $v = db_escape($v); }    # Escaping parameters
        # str_replace - replacing ? -> %s. %s is ugly in raw sql query
        # vsprintf - replacing all %s to parameters
        $sql_query = vsprintf( str_replace("?","%s",$query), $params );
        $sql_query = mysql_query($sql_query);    # Perfoming escaped query
    } else {
        $sql_query = mysql_query($query);    # If no params...
    }

    return ($sql_query);
}

/**
 * Automatically adds quotes (unless $quotes is false), but only for strings. Null values are converted to mysql keyword "null", booleans are converted to 1 or 0, and numbers are left alone.
 * Also can escape a single variable or recursively escape an array of unlimited depth.
 */
function db_escape($values, $quotes = true) {
    if (is_array($values)) {
        foreach ($values as $key => $value) {
            $values[$key] = db_escape($value, $quotes);
        }
    }
    else if ($values === null) {
        $values = 'NULL';
    }
    else if (is_bool($values)) {
        $values = $values ? 1 : 0;
    }
    else if (!is_numeric($values)) {
        $values = mysql_real_escape_string($values);
        if ($quotes) {
            $values = '"' . $values . '"';
        }
    }
    return $values;
}
 

$result = mysql_safe("select 1 from table");
 

$result = mysql_safe("select ? from table where foo=?", array(1, "bar"));