zval.u1.type类型：
/* regular data types */
#define IS_UNDEF 0
#define IS_NULL 1
#define IS_FALSE 2
#define IS_TRUE 3
#define IS_LONG 4
#define IS_DOUBLE 5
#define IS_STRING 6
#define IS_ARRAY 7
#define IS_OBJECT 8
#define IS_RESOURCE 9
#define IS_REFERENCE 10
/* constant expressions */
#define IS_CONSTANT 11
#define IS_CONSTANT_AST 12
/* fake types */
#define _IS_BOOL 13
#define IS_CALLABLE 14
/* internal types */
#define IS_INDIRECT 15
#define IS_PTR 17