Home arrow PHP arrow Page 4 - Using Relevance Rankings for Full Text and Boolean Searches with MySQL

Building an additional example - PHP

If you're a web developer who is searching for a step-by-step guide on how to quickly implement full text and Boolean searches with MySQL, then look no further. This group of articles might be what you need. Welcome to the second tutorial of the series that began with "Performing Full Text and Boolean Searches with MySQL."

  1. Using Relevance Rankings for Full Text and Boolean Searches with MySQL
  2. Developing a basic MySQL-driven search engine
  3. Determining the 50 percent threshold
  4. Building an additional example
By: Alejandro Gervasio
Rating: starstarstarstarstar / 7
June 13, 2007

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In consonance with the concepts deployed in the previous section, the last example that I'm going to show you here will consist of demonstrating how MySQL is capable of returning different relevance rankings according to the search terms entered in a web form.

In this case, I'm going to use two concatenated search words to return a couple of relevance values from the previous "USERS" database table, instead of only one. I'm going to use the pair of source files that you learned in the beginning of the article, so here are their respective signatures:

(definition of form.htm file)

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
<html xmlns="http://www.w3.org/1999/xhtml">
<meta http-equiv="Content-Type" content="text/html; charset=iso-
8859-1" />
<title>Working with relevance results</title>
<style type="text/css">
padding: 0;
margin: 0;
background: #fff;

font: bold 16px Arial, Helvetica, sans-serif;

color: #000;

text-align: center;



font: bold 11px Tahoma, Arial, Helvetica, sans-serif;

color: #000;



width: 40%;

padding: 10px;

margin-left: auto;

margin-right: auto;

background: #6cf;





<h1>Working with relevance results</h1>

<div id="formcontainer">

<form action="search.php" method="get">

<p>Enter search term here : <input type="text" name="searchterm"
title="Enter search term here" /><input type="submit"
name="search" value="Search Now!" /></p>





(definition of search.php file)


// define 'MySQL' class

class MySQL{

private $conId;

private $host;

private $user;

private $password;

private $database;

private $result;

const OPTIONS=4;

public function __construct($options=array()){


throw new Exception('Invalid number of connection parameters');


foreach($options as $parameter=>$value){


throw new Exception('Invalid parameter '.$parameter);






// connect to MySQL

private function connectDB(){


throw new Exception('Error connecting to the server');



throw new Exception('Error selecting database');



// run query

public function query($query){


throw new Exception('Error performing query '.$query);


return new Result($this,$this->result);


public function escapeString($value){

return mysql_escape_string($value);



// define 'Result' class

class Result {

private $mysql;

private $result;

public function __construct($mysql,$result){




// fetch row

public function fetchRow(){

return mysql_fetch_assoc($this->result);


// count rows

public function countRows(){


return false;


return $rows;


// count affected rows

public function countAffectedRows(){


throw new Exception('Error counting affected rows');


return $rows;


// get ID form last-inserted row

public function getInsertID(){


throw new Exception('Error getting ID');


return $id;


// seek row

public function seekRow($row=0){


throw new Exception('Invalid result set offset');



throw new Exception('Error seeking data');





// connect to MySQL

$db=new MySQL(array


$result=$db->query("SELECT firstname, MATCH
(firstname,lastname,comments) AGAINST('$searchterm') AS
relevance FROM users");


echo 'No results were found.';



echo '<h2>Users returned are the following:</h2>';


echo '<p>Name: '.$row['firstname'].' Relevance: '.$row




catch(Exception $e){

echo $e->getMessage();




Now, after listing the two previous source files, please study the following results returned by MySQL after entering the search string "alejandro+susan" in the corresponding web form:

// PHP file displays the following:
Users returned are the following:
Name: Alejandro Relevance: 1.0167628961849
Name: John Relevance: 0
Name: Susan Relevance: 1.0277009445163
Name: Julie Relevance: 0

As you can see, in the previous case the search query has returned two different relevance rankings in accordance with the inputted search terms. Hopefully, this last example should give you a better idea of the way that MySQL handles relevance values.

As usual with many of my articles on PHP development, feel free to modify all the code samples shown here, so you can start quickly implementing full-text searches in your own web applications.

Final thoughts

In this second article of the series, I provided you with a basic introduction to using relevance rankings when performing full-text searches with MySQL. In the final part I'm going to complete this interesting subject by teaching you how to use Boolean operators with your search queries.

You've been warned, so don't miss it!

>>> More PHP Articles          >>> More By Alejandro Gervasio

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