Demo: PHP-MySQL database connection using namespaces

Namespace in PHP:-

Namespace concept isn’t any new for programmers coming from c++, java, python or ruby platform.  They are a way of encapsulating classes. You could compare it with package in other programming language, which contains several classes.

Advantages of PHP Namespaces:-

1. Prevents class collisions of different libraries.
2. Allow to use class alias to make code more readable.

Defining and importing Namespaces in PHP.

namespace DB; 
// here DB is declared as namespace any code come below will be encapsulated by it.

They can be separated by forward slashes.

namespace \FRAMEWORK\DB\MODELS; 
// but it doesn't mean class DB must reside inside  FRAMEWORK namespace.

Now to use it,

use \FRAMEWORK\DB\MODELS as model; 
// to import namespace in your application.

Example:- code readability with namespaces

use \DB\MySQL as mysql;

/**
* Creating a new database connection.
* new mysql() creates new Object
*/
$link = new mysql(array(
		'host' => 'localhost',
		'database' => 'curd',
		'username' => 'root',
		'password' => ''
		));

$DB = $link->getConnection()->connectDB();

$users = $DB->query("select * from users")->fetch();

See the database table structure for above code.

Using namespace in PHP code

We’ll have following file structure to arrange the namespace.

/demo.php
/config.php
/import/
/import/db.php
/import/db/
/import/db/mysql.php
/import/db/mysql/
/import/db/mysql/query.php

Make config file with global configuration:-

//File Location: /config.php

define("NAMESPACE_DIR",'import'); 

function __autoload($class) {     
$parts = explode("\\", $class);     
$filepath = implode(DIRECTORY_SEPARATOR,$parts);     
$filepath = strtolower(NAMESPACE_DIR.DIRECTORY_SEPARATOR.$filepath.'.php');     
require $filepath; 
} 

$DB_SETTINGS = array( 	
	'host' => 'localhost',
	'database' => 'curd',
	'username' => 'root',
	'password' => ''
);

global $DB_SETTINGS;

• Above code makes default setting for database connection.
• we made __autoload() function to specify php how it should load class files.
• In our example  __autoload() function looks into directory “import”.
• Then every namespace would be store as separate directory.
• classes within that namespace will be stored inside namespace  directory.

Example, see following code

use \DB\MySQL as mysql;

___autoload() will look for file into following location.

/import/db/mysql/mysql.php

Revisiting basic mysql functions

Create mysql class into DB package

//File Location: /import/db/mysql.php

namespace DB; 

class MySQL{

protected $host; 	
protected $database; 	
protected $username; 	
protected $password; 	
private $resource_id; 	
public $connection = NULL; 

function __construct($settings = array()) {
                $this->host          = $settings['host'];
		$this->database 	= $settings['database'];
		$this->username 	= $settings['username'];
		$this->password 	= $settings['password'];
                /**
                * if connection already created just return resource_id
                * else create new one
                */
		if( is_null($this->connection) ) {
			$this->getConnection()->connectDB();
		}

		return $this->connection;
	}

	function __destruct() {
		@mysql_close($this->connection);
	}

	public function getConnection(){
/** 
* Native php function to create db_connection
*/	
	$this->connection = @mysql_connect(
				$this->host,
				$this->username,
				$this->password
		);

		if(!$this->connection) {
			die("Unable to create connection, Server might be too busy or check your credentials!");			
		}

		return $this;
	}

	public function connectDB() {
/** 
* Native php function to select database
*/
		if(mysql_select_db($this->database,$this->connection)){
			return $this;
		} else {
			die("Unable to connect to database");
		}
	}

}

Create query class into MySQL package

//File Location: /import/db/mysql/query.php

namespace DB\Mysql; 
use DB\Mysql as mysql; 

class Query extends mysql{ 

private $resource_id; 	
private $record_set; 

function __construct( $sql ){ 		
  global $DB_SETTINGS; 		
  $this->record_set = Array();
		$this->resource_id = parent::__construct($DB_SETTINGS);	
		$this->query($sql);
	}

	public function query($sql) {
			$this->resource_id = mysql_query($sql,$this->connection);
			if(!$this->resource_id){
				echo (mysql_error());
				return null;
			}
			return $this;
	}

	public function fetch() {
			$record_set = Array();
			while($row = mysql_fetch_assoc($this->resource_id)) {
				$record_set[] = $row;
			}
			return $record_set;
	}	
}

Creating demo.php file

// File Location: /demo.php

require("config.php"); 

use DB\MySQL\Query as query; 

$users = new query("select * from users"); 
$all_users = $users->fetch(); 

foreach ($all_users as $user): 	
         print $user['name'] . "  ";  	
         print $user['email'] . ""; 
endforeach;

You could download sample working code here. In upcoming post I’ll explain how to plug mysqli class to this DB package without changing core business logic.