I was wondering when I should use static methods and properties instead of 'normal' properties and methods. I know that static methods can be called without creating an instance of an object but I can't seem to find another example when to use static methods or properties.
Can somebody explain the static keyword with some examples how and when to use it (or not)?
Values of static proptery's are shared over all classes of the same type:
class foo{
static $bar;
function __construct($set = null){
if($set){
self::$bar = $set;
}
echo self::$bar;
}
}
$a = new foo(1); // 1
$b = new foo(); // 1
They are very useful to hold (for example) a resources to share across the entire class, like a database connection. It can also be used for keeping statistics on how many calls have been made to a specific function, etc.
Now static methods are useful for keeping a code grouped inside the same scope, interacting with the class that may not need the instance of the class to function.
They may for example return a static variable that holds an instance of a class. Because they are essentially methods, they are bound to follow interfaces and you can force a class to have a static method called getInstance() to have the same flow as other one-time classes. (hint, it works great with traits)
Static methods are handy when the method doesn't change the state of the object.
class yourMom{
public $name;
function __construct($name, $ageInYears){
$this->name = $name;
$this->age_in_days = self::yearsToDays($ageInYears);
}
private static yearsToDays($years){
return 365 * $years;
}
}
In this example it's basically a helper function.
