Counter

[zorgi]

Hi everyone

I wrote small counter class. It counts number of daily visits. It remembers all ip addresses per page and counts them only once within any 24 hours per page and it works fine. Here is the code:

class Counter{
    private static $instance;
    public static $path = "Counter";
    private $visits = array();
    private $ip_reg = array();
    private $current_date;
 
 
    private function __constructor(){
        $this -> $current_date = date("m.d.y");            
    }
 
    public static function getFileInstance(){        
        if(file_exists(self::$path)){
            self::$instance = (unserialize(file_get_contents(self::$path)));
        }else{
            self::$instance = new Counter();
        }
 
        return self::$instance;
    }
 
    private function saveFileInstance(){
        file_put_contents(self::$path, serialize(self::$instance));    
    }
 
    private function addVisit(){
        if(isset($this -> visits[$_SERVER['PHP_SELF']])) {
            $this -> visits[$_SERVER['PHP_SELF']] += 1;
        }else{
            $this -> visits[$_SERVER['PHP_SELF']] = 1; 
        }                        
    }
 
    private function register_ip(){
        if($this -> current_date != date("m.d.y")){
            $this -> ip_reg = array();
            $this -> current_date = date("m.d.y");
        }
 
        $ip_adr = $_SERVER['REMOTE_ADDR'];
 
        if($this -> ip_reg[$ip_adr][$_SERVER['PHP_SELF']] != 1){
            $this -> ip_reg[$ip_adr][$_SERVER['PHP_SELF']] = 1;
            $this -> addVisit();
            $this -> saveFileInstance();                        
        }    
        $this -> printCounter();    
    }
 
    private function printCounter(){
        echo $this -> visits[$_SERVER['PHP_SELF']];
    }
 
    public function run(){
        $this -> register_ip();
    }
}
 

My question is what happens if I get 2 visits at the same time. They will get 2 identical instances of the class and obviously one visit will not be recorded. I know its not major issue but am just curious about possible solutions to this problem.

Thanx

[Dormilich]

@zorgi
I don't think that the 2nd visit gets dropped, because the server would rather queue the http request than dropping it. or in other words: 2 requests = 2 processor threads = running the code seperately. (despite the fact, that "same time" means exactly at the same microsecond)

note on code:
I assume you want it to be a singleton, __construct() must be empty (same goes for __clone())! otherwise you can create new instances outside the class.

the difference between "private function __construct()" and "public function __construct()" is:

class test extends Counter
{
    function __construct()
    {
        # works not with private declaration
        parent::__construct();
    }
}

another way to create the singleton's instance:

self::$instance = new self;

and some speedup:
if you're fine with the timestamp (instead of the date), you can read it from the superglobals

$this->$current_date = $_SERVER["REQUEST_TIME"];

[zorgi]

@Dormilich

Hi Dormilich
Thank you for the pointers.

Yes I wanted to create singleton and am puzzled now. Are you saying that even I declared constructor as private I can still do this: new Counter();
from outside the class just because constructor is not empty?

[zorgi]

@zorgi
Oh thought about it bit more and figured it out... Thanks again :)

[Dormilich]

@zorgi
of course, you do it all the time (line #17). that is not a call inside the class (by means of $this-> or self::). magic methods do not work like ordinary methods (compare it with magic constants).

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