Self-Generating Class Objetcs in PHP

I have a directory on the webserver in my development environment where I do little experiments. I try out stuff that I cant figure out by looking into the PHP documentation – either because I can’t find the right place to look or because it’s just not explained.

Sadly I need to use that directory quite often. Almost daily.

Today I found this little gem:

$x->y->z = 123;
echo $x->y->z;

Without trying, what would you guess what happens when I try to set a value to a property of a property of a variable that I never initialized with an object?

I thought, this would fail and quit with some kind of error message. But no: This script prints „123“.

When I add a print_r($x) to my code I get this:

stdClass Object
    [y] => stdClass Object
            [z] => 123


That means that PHP creates an object for me when I try to access properties of a variable that is not set, yet.

So: What happens when the variable HAS a value before I try to set a property?
I have to answer with „Well, that depends…“

  • If the variable is NULL or an empty string (!), an object will be auto-generated
  • If the variable is numeric (including „0“ (!)) or a string with a length of at least 1 character nothing happens at all. No error message, nothing.
  • If the variable already is an object, nothing needs to be done. But note that if the object has no property of the given name, a property is added automatically

I find it quite strange that an empty string seems to be handled the same way as NULL while the numeric value 0 is not.

Another magic behavior uncovered… Let’s see what comes next…