One of your templates is trying to print the value of a variable or expression
and, instead of a string, it's a PHP object of type
stdClass. Since it's
uncommon to use that PHP class directly, this may be the result of some other
operation in PHP code.
For example, you may have used
json_decode('...') without passing
the second argument. That makes the result to include
stdClass objects instead
of being a PHP associative array.