PHP中Zval是什么

struct _zval_struct {

    union {

        zend_long         lval;             /* long value */

        double            dval;             /* double value */

        zend_refcounted  *counted;

        zend_string      *str;

        zend_array       *arr;

        zend_object      *obj;

        zend_resource    *res;

        zend_reference   *ref;

        zend_ast_ref     *ast;

        zval             *zv;

        void             *ptr;

        zend_class_entry *ce;

        zend_function    *func;

        struct {

            uint32_t w1;

            uint32_t w2;

        } ww;

    } value;

    union {

        struct {

            ZEND_ENDIAN_LOHI_4(

                zend_uchar    type,         /* active type */

                zend_uchar    type_flags,

                zend_uchar    const_flags,

                zend_uchar    reserved)     /* call info for EX(This) */

        } v;

        uint32_t type_info;

    } u1;

    union {

        uint32_t     var_flags;

        uint32_t     next;                 /* hash collision chain */

        uint32_t     cache_slot;           /* literal cache slot */

        uint32_t     lineno;               /* line number (for ast nodes) */

        uint32_t     num_args;             /* arguments number for EX(This) */

        uint32_t     fe_pos;               /* foreach position */

        uint32_t     fe_iter_idx;          /* foreach iterator index */

    } u2;

};