Setting up a concrete example: putting the "DataCompressor" class to work - PHP

In order to demonstrate in a friendly way how the "DataCompressor" class can be used within an object-oriented development environment, I'll use the same "sample_file.php" file that you saw in my previous tutorial. As you'll recall, it displayed some rows from a "users" database table. In addition, I'll list the two MySQL processing classes used by this sample file. The example begins by showing both MySQL-related classes:

// define 'MySQL' class
class MySQL{
    private $host;
    private $user;
    private $password;
    private $database;
    private $connId;
    // constructor
    function __construct($options=array()){
        if(!is_array($options)){
            throw new Exception('Connection options must be an
array');
        }
        foreach($options as $option=>$value){
            if(empty($option)){
                throw new Exception('Connection parameter cannot
be empty');
            }
            $this->{$option}=$value;
        }
        $this->connectDb();
    }
    // private 'connectDb()' method
    private function connectDb(){
        if(!$this->connId=mysql_connect($this->host,$this-
>user,$this->password))
{
            throw new Exception('Error connecting to MySQL');
        }
        if(!mysql_select_db($this->database,$this->connId)){
            throw new Exception('Error selecting database');
        }
    }
    // public 'query()' method
    public function query($sql){
        if(!$result=mysql_query($sql)){
            throw new Exception('Error running query '.$sql.'
'.mysql_error());
        }
        return new Result($this,$result);
    }
}
// define 'Result' class
class Result{
    private $mysql;
    private $result;
    // constructor
    public function __construct($mysql,$result){
        $this->mysql=$mysql;
        $this->result=$result;
    }
    // public 'fetch()' method
    public function fetch(){
        return mysql_fetch_array($this->result,MYSQL_ASSOC);
    }
    // public 'count()' method
    public function count(){
        if(!$rows=mysql_num_rows($this->result)){
            throw new Exception('Error counting rows');
        }
        return $rows;
    }
    // public 'get_insertId()' method
    public function getInsertId(){
        if(!$insId=mysql_insert_id($this->mysql->connId)){
            throw new Exception('Error getting insert ID');
        }
        return $insId;
    }
    // public 'seek()' method
    public function seek($row){
        if(!int($row)&&$row<0){
            throw new Exception('Invalid row parameter');
        }
        if(!$row=mysql_data_seek($this->mysql->connId,$row)){
            throw new Exception('Error seeking row');
        }
        return $row;
    }
    // public 'getAffectedRows()' method
    public function getAffectedRows(){
        if(!$rows=mysql_affected_rows($this->mysql->connId)){
            throw new Exception('Error counting affected rows');
        }
        return $rows;
    }
    // public 'getQueryResource()' method
    public function getQueryResource(){
        return $this->result;
    }
}

Now that you've hopefully recalled how the above MySQL processing classes looked, it's time to list the corresponding "sample_file.php" file. Here's the respective definition for this file:

try{
    // include class files
    require_once 'mysqlclass.php';
    require_once 'resultclass.php';
    // connect to MySQL
    $db=new MySQL(array
('host'=>'host','user'=>'user','password'=>'password',
'database'=>'database'));
    // run SQL query
    $result=$db->query('SELECT * FROM users');
    // display results
    while($row=$result->fetch()){
        echo $row['id'].$row['name'].$row['email'].'<br />';
    }
}
catch(Exception $e){
    echo $e->getMessage();
    exit();
}

As the above example clearly shows, the "sample_file.php" file first includes the corresponding MySQL processing classes, in order to connect to the MySQL server, and then performs a simple SELECT statement to fetch a few rows from a sample "users" database table. Once the database rows have been returned by the query, they're simply displayed on the browser, as one expects when proceeding with a regular MySQL result set.

Of course, since I'm currently using PHP 5 as my testing platform, the whole code is wrapped by a single "try-catch" block, in order to trap all the potential exceptions that could eventually be triggered by the different sections of the script. As you can see, all the tasks performed by the "sample_file.php" file are very understandable.

Now that you clearly understand how the previous sample file works, take a look at the following piece of code, which demonstrates a practical implementation for the "DataCompressor" class:

try{
    // instantiate a new 'DataCompressor' object
    // pass the 'sample_file.php' file in order to compressing
its dynamic output
    $dataComp=new DataCompressor('sample_file.php');
    // send Gzip http header
    $dataComp->sendEncodingHeader();
    // uncompress & display data
    echo $dataComp->fetchCompressedData();
}
// catch all possible exceptions
catch(Exception $e){
    echo $e->getMessage();
    exit();
}

If you study the example shown above, then you'll definitely agree with me that using the "DataCompressor" class is really a simple and straightforward process.