Not yet possible to assign complex types to properties.
Came across something new (for me anyway) today. I was using PHP5′s SimpleXML functions to grab youtube video data so I could make automatic posts (and attach youtube comments) in wordpress based off a video’s ID. At some point I was passing what I thought was a variable into an array that was then later being manipulated by a native wordpress function during the comment post processing. While the code itself was actually working and attaching the comments to the posts, I was getting a weird error on each insert that was warning me about assigning complex types to properties, something I had never seen before.
A stackoverflow post on Forcing a SimpleXML Object to a String was the guiding light I needed.
The Error
Warning: It is not yet possible to assign complex types to properties in wp-includes\formatting.php on line 1234
The Solution
Typecast the object as a string before attempting to manipulate it.
$foo = array( (string) $xml->channel->item->title );