PHPLIB-808: Leave fullDocument change stream option unset by default (#901)
PHPLIB-808: Leave fullDocument change stream option unset by default (#901)

array_key_exists function is used to avoid case when array field "fullDocument" with NULL value is passed from input (there is already exists an incorrect NULL-value input data test in MongoDB\Tests\Operation\WatchTest:55)
jmikola/mongo-php-library,mongodb/mongo-php-library,jmikola/mongo-php-library,mongodb/mongo-php-library,jmikola/mongo-php-library,jmikola/mongo-php-library,jmikola/mongo-php-library-prototype,mongodb/mongo-php-library,mongodb/mongo-php-library