PHP: Example of OOP - Database Class

One of the common nightmares for developers is to maintain repeated code in a single program which happen to be declared over and over again. Basically, what I'm trying to say is that it is frustrating to mae simple changes on the code yet finding yourself debugging the program due to since there are so many untracked code. Thanks to immersion of Object Oriented Programming which lessen the bummer by introducing the DRY (Don't Repeat Yourself). A tenet that allows you to group similar tasks into classes to avoid repeatition and make an easy maintain code. It also save your time since you don't need to keep declaring your code over and over again. If you haven't learn OOP, it's time for you to step up, you can visit and learn more about PHP Objected Oriented Programming by the following resources.

http://en.wikipedia.org/wiki/Object-oriented_programming
http://net.tutsplus.com/tutorials/php/object-oriented-php-for-beginners/
http://php.net/manual/en/language.oop5.php

I have here an example of OOP code and please be reminded that this is only for demonstration purposes. This class is called "Database". It allows you to query, fetch record etc... by using the methods defined on the class.

First File:

<?php
class Database 
{ 
 public $host     = "hostname";
 public $database = "databasename"; 
 public $username = "username"; 
 public $password = "password"; 
 public $conId    = 0;  
 public $queryId  = 0;  
    public $record   = array();  
    public $row;          
    public $errNo    = 0; 
    public $error    = ""; 
    
 //call connection method upon constructing 
 public function __construct(){
  $this->createConnection(); 
 }
 
 //connection to the database
 public function createConnection() 
    { 
        if( 0 == $this->conId ) 
            $this->conId=mysql_connect( $this->host, $this->username, $this->password ); 
        if( !$this->conId ) 
   $this->stopExec( "Trying to connect.... Result: failed" ); 
        if( !mysql_query( sprintf( "use %s", $this->database ), $this->conId ) ) 
            $this->stopExec( "cannot use database ".$this->database ); 
 } 

 //execute query string 
 public function query($queryString) 
    { 
  $this->queryId = mysql_query( $queryString, $this->conId ); 
        $this->row = 0; 
        $this->errNo = mysql_errno(); 
        $this->error = mysql_error(); 
        if(!$this->queryId ) 
   $this->stopExec( "Invalid SQL String: ".$queryString ); 
  return $this->queryId; // return the resource id of query. You can either then call fetchRecord method. 
    } 
 
 public function fetchRecord($type = 1)
 { 
  //1 --> for array
  //2 --> for object
  if($type == 1){
   $record = mysql_fetch_array($this->queryId); //return array
  }else{
   $record = mysql_fetch_object($this->queryId); //return object
  }
  
  return $record;
 }
 //stop the execution of query when there's an error
 public function stopExec( $msg ) 
 { 
  printf( "Database error: %s <br>n", $msg ); 
  printf( "MySQL Error: %s (%s)<br>n", $this->errNo, $this->error ); 
 } 
 
 //get the number of row
 public function numRows() 
 { 
  return mysql_num_rows( $this->queryId ); 
 } 
         
} 

?>

To try the code above. Save it as "database.php" then create another php file and paste the code below. Make sure that the two files are on the same directory and you had change the following variable values on the database class.

 public $host     = "hostname";
 public $database = "databasename"; 
 public $username = "username"; 
 public $password = "password"; 

Second file:

<?php
include('database.php');
$db = new Database();
$sql = "SELECT * from tablename"; 
$db->query($sql);
print_r($db->fetchRecord(1));
?>

Since, it is only for demonstration, it is not advisable to use this code for big project because of insufficiency. Using ORM (Object Relation Mapping) is still the best way in managing database in larger project. Although you can still use this is small scale project provided that you still need to edit their visibility properties etc. I hope this somewhat helpful to all.