PHP源码分析之变量的存储过程分解(2)

#define ZEND_SET_SYMBOL(symtable, name, var)          \   {                                                     \ 
        char *_name = (name);                         \ 
        ZEND_SET_SYMBOL_WITH_LENGTH(symtable, _name, strlen(_name)+1, var, 1, 0);   \ 
} 
//主要的实现为下面这个函数： 
#define ZEND_SET_SYMBOL_WITH_LENGTH(symtable, name, name_length, var, _refcount, _is_ref)                                                       \ 
    {                                                                        
        zval **orig_var;                                        \  
        if (zend_hash_find(symtable, (name), (name_length), (void **) &orig_var)==SUCCESS                                                         \ 
            && PZVAL_IS_REF(*orig_var)) {                     \ 
            (var)->refcount = (*orig_var)->refcount;                  \ 
            (var)->is_ref = 1;                                \ 
            if (_refcount) {                                      \ 
                (var)->refcount += _refcount-1;               \ 
            }                                             \ 
            zval_dtor(*orig_var);                             \ 
            **orig_var = *(var);                                  \ 
            FREE_ZVAL(var);                               \ 
        } else {                                              \ 
            (var)->is_ref = _is_ref;                              \ 
            if (_refcount) {                                      \ 
                (var)->refcount = _refcount;                      \ 
            }                                             \ 
            zend_hash_update(symtable, (name), (name_length), &(var), sizeof(zval *), NULL);                                                           \ 
        }                                                  \ 
    }            

该函数的功能是：
1. 如果全局符号表已经存在该变量且是引用类型，则