Lazy Instantiation

lazy-instantiation.php

<?php

class LazyInstantiation {
	
	// we can only access this static property
	// through the public static getter since 
	// the property is private
	private static $expensive_to_compute;
	
	// public static getter
	public static function get_expensive_to_compute(){
		
		if( self::$expensive_to_compute === null ){ // or empty()
			
			// only instantiate once
			self::$expensive_to_compute = some_function_that_is_expensive();
		}
		
		return self::$expensive_to_compute;
	}
}