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Andrial12 03-23-2009 01:13 PM
Classes and MySQLi
 
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);
    }
    
}


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