Since PHP is a loosely typed language, it provides great flexibility in creating variables and objects at runtime without having to specifically declare them first. It is well known that $i=10, $i=”test”, $i = date() will all work without creating any syntax or compile errors.

A lesser used concept is that this feature can be used to create an object at runtime without having to check for the object type at first. Eg.if you have had 3 classes and only one of them had to be created depending on a condition the following would be the sample code:

<?php
	error_reporting(E_ALL);

	class Generic {
		function xprint() {
			echo("generic");
		}
	}
	class A extends Generic{
		function xprint() {
			echo("A");
		}
	}

	class B extends Generic{
		function xprint() {
			echo ("B");
		}
	}

	class C extends Generic{
		function xprint() {
			echo("C");
		}
	}

	$test = "B";
	if ($test =="B")
		$x = new B();
	else if ($test == "A"
		$x = new A();
    else if ($test == "C")
	    $x = new C();
	$x->xprint();
	echo("end");
?>

Instead of doing multiple checks and then creating the relevant class, a more efficient way is to pass the classname as a string and then create it directly as shown below:

<?php
	error_reporting(E_ALL);

	class Generic {
		function xprint() {
			echo("generic");
		}
	}
	class A extends Generic{
		function xprint() {
			echo("A");
		}
	}

	class B extends Generic{
		function xprint() {
			echo ("B");
		}
	}

	class C extends Generic{
		function xprint() {
			echo("C");
		}
	}

	$test = "B";
	$x = new $test();
	$x->xprint();
	echo("end");
?>

The above code will print “B” since it creates the class B in $x. What about classes where arguments are required in the constructor? Simple call it with the arguments eg. $x = new $test(“arg1″, “arg2″);