PHP扩展 怎么访问常量属性

请问：在php扩展中用zend_declare_class_constant_stringl定义的常量属性 怎么访问？ 我用zend_read_static_property和zend_read_property都不行？

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ZEND_API int zend_get_constant(const char *name, uint name_len, zval *result TSRMLS_DC);
ZEND_API int zend_get_constant_ex(const char *name, uint name_len, zval *result, zend_class_entry *scope, ulong flags TSRMLS_DC);