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…

Eine Antwort auf „Self-Generating Class Objetcs in PHP“

While that is true, do note that when the E_STRICT error level is set (which I *always* have set during development or testing) it returns a „Strict notice: creating standard object from empty value.“

Something like this (untested) would solve that issue:


class standardClass extends stdClass
{

	public function __get( $index )
	{
	
		if( !isset( $this->$index ) || !$this->$index instanceof stdClass )
		{
			$this->$index = new standardClass();
			return $this->$index;
		}
		else
		{
			return $this->$index;
		}
		
	}
	
}

$x = new standardClass();
$x->y->z = 123;
print_r( $x );

If the above code is unreadable, check pastebin: http://pastebin.com/PcfGakyM

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