PHP Singleton PDO

Question

from http://www.php.net/manual/en/class.pdo.php

###### config.ini ######
db_driver=mysql
db_user=root
db_password=924892xp

[dsn]
host=localhost
port=3306
dbname         


        

Answer 1

A single ton is a static function that allows you to keep track of your object instances, when you use a singleton you create an instance of the object but the instances always stays with the associated object.

Take this example:

$db1 = new Database();
$db2 = new Database();

as you can see that db1 and db2 are 2 new instances of Database therefore there not the same, now take this example.

$db1 = Database::Instance();
$db2 = Database::Instance();

And the code for Instance

class Database
{
    private static $_instance;

    public static Instance()
    {
        if(self::$_instance !== null)
        {
            //We have already stored the object locally so just return it.
            //This is how the object always stays the same
            return self::$_instance;
        }
        return self::$_instance = new Database(); //Set the instance.
    }
}

If you analyse the code you will so that no matter where you use Instance throughout your application your object will always be the same.

a static function is a method within a class/object isa type of method that can be used without the object being initialized.

In regards to __callStatic method, this is a Magic Method that's executed where a static method is not available.

For example:

class Database
{

    public static function first()
    {
        echo 'I actually exists and I am first';
    }

    public function __callStatic($name,$args)
    {
        echo 'I am '. $name .' and I was called with ' . count($args) . ' args';
    }
}

lets test them.

Database::first(); //Output: I actually exists and I am first

Database::second(); //Output: I am second and I was called with 0 args

Database::StackOverflow(true,false); //Output: I am StackOverflow and I was called with 2 args

Hope this helps you