How can I solve "Non-static method xxx:xxx() should not be called statically in PHP 5.4?

You can either remove E_STRICT from error_reporting(), or you can simply make your method static, if you need to call it statically. As far as I know, there is no (strict) way to have a method that can be invoked both as static and non-static method. Also, which is more annoying, you cannot have two methods with the same name, one being static and the other non-static.

Disabling the alert message is not a way to solve the problem. Despite the PHP core is continue to work it makes a dangerous assumptions and actions.

Never ignore the error where PHP should make an assumptions of something!!!!

If the class organized as a singleton you can always use function getInstance() and then use getData()

Likse:

$classObj = MyClass::getInstance();
$classObj->getData();

If the class is not a singleton, use

 $classObj = new MyClass();
 $classObj->getData();

I don't suggest you just hidding the stricts errors on your project. Intead, you should turn your method to static or try to creat a new instance of the object:

$var = new YourClass();
$var->method();

You can also use the new way to do the same since PHP 5.4:

(new YourClass)->method();

I hope it helps you!