Cursor::__toString() uses RETVAL_LONG() to convert the cursor ID to a string. On a 32-bit platform, the uint64_t cannot be fully represented in the zval, which makes this an inaccurate conversion. We should use the same logic found in UTCDateTime::__toString() (i.e. sprintf() with an type-appropriate pattern).

Similarly, var_dump() needs to print the cursor ID as a string on 32-bit platforms. It currently uses an integer on all platforms.