PHP underlying variables

In the zend.h in the Zend directory, you will find that the variables are defined like this

typedef Union _ZVALUE_VALUE {
Long lval;/* Long value */
Double dval;/* Double Value */
struct {
Char *val;
int Len;
} str;
HashTable *ht;/* Hash Table value */
Zend_object_value obj;
Zend_ast *ast;
} Zvalue_value;

struct _zval_struct {
/* Variable Information */
Zvalue_value value;/* Value */
Zend_uint refcount__gc;
Zend_uchar type;/* Active Type */
Zend_uchar is_ref__gc;
};

Zval structure is the variable of PHP

A total of 4 member variables

Value is the reference number of the variable refcount__gc the variable, the type of the variable, is_ref__gc whether the struct type of the value corresponds to the _zvalue_value of the previous union

The Zend engine defines the following variable types PHP version (5.6.8)

PHP underlying variables