How can I create dynamically objects based on array values in php?

Question

I'ld like to dynamically create as many object as present in my $instance array (e.g. domain1_com and domain2_com) and give them the name of array value (e.g. domain1_com and domain2_com) so I can access it through these names (e.g. domain1_com->example()).

Is it possible? I tried something like this but obviously doesn't work.

    class myClass
    {
        public static function getInstances()
        {
            // I connect to the database and execute the query
            $sql = "SELECT * FROM my_table";    
            $core = Core::getInstance();
            $stmt = $core->dbh->prepare($sql);

            if ($stmt->execute()) {
                $results = $stmt->fetchAll(PDO::FETCH_ASSOC);
            }

            // Read values in my array
            foreach ($results as $instance) {

                $obj = $instance["domain"]);
                // return 2 values: domain1_com and domain2_com

                $obj = new myClass();
            }
        }

        public function example()
        {
            echo "This is an instance";
        }
    }

    myClass::getInstances();

    $domain1_com->example();
    $domain2_com->example();

Sergiu Paraschiv · Accepted Answer · 2015-01-24 16:47:35Z

2

You can use variable variables.

$name = "foo";
$$name = new bar();

is the same as

$foo = new bar();

You cannot access the variables created inside getInstances outside of that method. They are local, not global.

Try this code:

class myClass
{
    public static function getInstances()
    {
        $results = array('domain1_com', 'domain2_com');

        foreach ($results as $instance) {
            $$instance = new myClass();
            // This is equivalent to "$domainX_com = new myClass();".
            // Writing that code here would define a _local_ variable named 'domainX_com'.
            // This being a method inside a class any variables you define in here are _local_,
            // so you can't access them' _outside_ of this method ('getInstances')
        }

        // this will work, we are inside 'getInstances'
        $domain1_com->example();
        $domain2_com->example();
    }

    public function example()
    {
        echo "This is an instance";
    }
}

myClass::getInstances();

// this won't work. $domainX_com are not accessible here. they only exist _inside_ 'getInstances'
// It's basic OOP.
// so this code will crash
$domain1_com->example();
$domain2_com->example();

It will produce this output:

This is an instance

This is an instance

E_NOTICE : type 8 -- Undefined variable: domain1_com -- at line 32

E_ERROR : type 1 -- Call to a member function example() on a non-object -- at line 32

You need a way to access those variables. I'd use this:

class myClass
{
    private static $instances = array();
    public static function getInstances()
    {
        $results = array('domain1_com', 'domain2_com');

        foreach ($results as $instanceName) {
            self::$instances[$instanceName] = new myClass();
        }
    }

    public static function getInstance($instanceName) {
        return self::$instances[$instanceName];
    }

    public function example()
    {
        echo "This is an instance";
    }
}

myClass::getInstances();

// this will work
myClass::getInstance('domain1_com')->example();
myClass::getInstance('domain2_com')->example();

edited Jan 24, 2015 at 16:47

answered Jan 24, 2015 at 16:01

Sergiu Paraschiv

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6 Comments

KaMZaTa Over a year ago

Thank you, but I can't still access to the objects

Sergiu Paraschiv Over a year ago

what do you mean? you access them the same way you instantiated them.

KaMZaTa Over a year ago

From outside of the class if I do $domain1_com->example() for example it doesn't show me nothing

Sergiu Paraschiv Over a year ago

of course you are not able to access a local variable inside a class method from outside that class. that's basic oop. you need to expose the new instances of 'class example' as public properties (or maybe a getter function) of myClass.

KaMZaTa Over a year ago

Thank you but I don't understand well what you mean. How can I expose outside my brand new instances created inside my static method? Can you do an example?

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