Scalar Value Types

.proto type	encoding	php type
double		string
float		string
int32	varint	string
int64	varint	string
uint32	varint	string
uint64	varint	string
sint32	zigzag+varint	string
sint64	zigzag+varint	string
fixed32		string
fixed64		string
sfixed32		string
sfixed64		string
bool		bool
string	utf8 string	string
bytes		string

Note: PHP's numeric value is platform dependant. Unfortunately long is 32bit value on some 64bit platform. It's impossible to keep precision for many types with PHP. so we use string types. it's safe. Don't forget. You have to use GMP or BCMath for calculating values which exceeds PHP_INT_MAX.

maybe I'll re-support long values for performance reason. but it can't handle big values correctly.