Whenever you got this error check the following:
1. Make sure the $this-> is used inside the object and referring to the class’s and inherited non-static members.
2. Make sure the called members of the object are properly addressed as static or member/function variables
Do you know the different different post types?
Here is an example for the second one.
Assume you have the following object
class Example
{
function getExampleText()
{
return "Example Text";
}
static function getStaticExampleText()
{
return "Static Example Text";
}
}
While accessing, if the code tries something like this one,
$example = new Example();
Example::getExampleText(); //Trying to access non-static as static
Then you would have the error