Classes and MySQLi

Andrial12 · 03-23-2009, 01:13 PM

I think its me missing a one of the major crux's of Object Orientated programming, but I've been looking for an answer to this problem for years now, and I've never been able to get a clear cut answer.

Here's a class that i've written:

PHP Code:


			
class model_element {

    

    var $id         = 0;

    var $name         = NULL;

    var $xml         = NULL;

    var $date         = NULL;

    var $type         = NULL;

    var $priority    = 0;



    function __construct($elements_id) {

    

        if(!empty($elements_id)) {

            $object_database = new mysqli(CONFIG_DATABASE_SERVER, CONFIG_DATABASE_USER, CONFIG_DATABASE_PASS, CONFIG_DATABASE_NAME_DEFAULT);

            

            $object_result = $object_database->query("

                SELECT

                    le.`elements_id`,

                    le.`elements_name`,

                    le.`elements_xml`,

                    le.`elements_date`,

                    le.`elements_type`,

                    le.`elements_priority`

                FROM

                    `lib_elements` AS le

                WHERE

                    le.`elements_id` = " . $elements_id . "

                ;

            ");

            

            $object_row = $object_result->fetch_object();

            

            $this->id             = $object_row->elements_id;

            $this->name         = $object_row->elements_name;

            $this->xml            = $object_row->elements_xml;

            $this->date         = $object_row->elements_date;

            $this->type         = $object_row->elements_type;

            $this->priority     = $object_row->elements_priority;

        }

        

    }

    

}

Now this class will need to be called a few (5 - 20) times of the course of loading one page.

Now everytime this class is initiated the database connection is restarted.

PHP Code:


			
$object_database = new mysqli(CONFIG_DATABASE_SERVER, CONFIG_DATABASE_USER, CONFIG_DATABASE_PASS, CONFIG_DATABASE_NAME_DEFAULT);

Which i'm sure in not the best way to got about things.

So what am i missing about using a database in an Object Orientated fashion should model_element extend mysqli? Or is that wrong aswell.

Thanks for any help in advance.

Oli.

Andrial12 · 03-23-2009, 03:48 PM

It was actually pretty easy once I really thought about it. What i needed to do was call initiate MySQLi via a child class which uses the singleton pattern.

Somebody will Probably find this quite useful.

database.php

PHP Code:


			
class database extends mysqli { 

    

    private static $instance = null; 

    

    private function __construct($database_server, $database_user, $database_pass, $database_name) { 

        @parent::__construct( 

            $database_server, 

            $database_user, 

            $database_pass, 

            $database_name

        ); 

        if(mysqli_connect_errno()) { 

            die('Could not Connect to database');

        } 

    } 

        

    public function getInstance($database_server, $database_user, $database_pass, $database_name) { 

        if(self::$instance === null) { 

            $c = __CLASS__; 

            self::$instance = new $c($database_server, $database_user, $database_pass, $database_name); 

        } 

        return self::$instance; 

    } 

    

    public function __clone() {

        die("Cannot clone ".__CLASS__." class"); 

    } 



}

model_element.php

PHP Code:


			
class mdl_element {

        

    var $id         = 0;

    var $name         = NULL;

    var $xml         = NULL;

    var $date         = NULL;

    var $type         = NULL;

    var $priority    = 0;



    function __construct($elements_id) {

    

        if(!empty($elements_id)) {

                

            $object_result = database::getInstance(CONFIG_DATABASE_SERVER, CONFIG_DATABASE_USER, CONFIG_DATABASE_PASS, CONFIG_DATABASE_NAME_DEFAULT)->query("

                SELECT

                    le.`elements_id`,

                    le.`elements_name`,

                    le.`elements_xml`,

                    le.`elements_date`,

                    le.`elements_type`,

                    le.`elements_priority`

                FROM

                    `lib_elements` AS le

                WHERE

                    le.`elements_id` = " . $elements_id . "

                ;

            ");

                

            $object_row = $object_result->fetch_object();

                

            $this->id             = $object_row->elements_id;

            $this->name         = $object_row->elements_name;

            $this->xml            = $object_row->elements_xml;

            $this->date         = $object_row->elements_date;

            $this->type         = $object_row->elements_type;

            $this->priority     = $object_row->elements_priority;

        }

        

    }

        

}

controller_element.php

PHP Code:


			
class ctl_element {



    var $element = array();

        

    function __construct($elements_id) {

        $this->element[] = new mdl_element($elements_id);

    }

        

    function display($xslt) {

        $xml =  "";

        $xml_temp = '<element language="en-GB"><id>0</id>' . $this->element[0]->xml;

        $xml_temp .= '<children>';

        for($i=0;$i<count($this->element[0]->children->children);$i++) {

            

            $xml_temp .= "<child>";

            $xml_temp .= $this->element[0]->children->children[$i]['xml'];

            $xml_temp .= "</child>";

            

        }

        $xml_temp .= '</children>';

        $xml_temp .= '</element>';

        $xml = '<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE exams SYSTEM "*DEAD LINK*"><exams>' . $xml_temp . '</exams>';

        

        return vw_createhtml($xml, $xslt);

    }

    

}