Zend/zend_constants.htypedef struct _zend_constant {	    zval value; /* zval结构，PHP内部变量的存储结构 */	    int flags;  /* 常量的标记如 CONST_PERSISTENT | CONST_CS */	    char *name; /* 常量名称 */	    uint name_len; /* 名称长度 */	    int module_number;  /* 模块号 */} zend_constant;

php的define函数

Zend/zend_builtin_functions.c

c.value = *val;zval_copy_ctor(&c.value);if (val_free) {	zval_ptr_dtor(&val_free);}c.flags    = case_sensitive; /* non persistent */c.name     = zend_strndup(name, name_len);c.name_len = name_len+1;c.module_number = PHP_USER_CONSTANT;if (zend_register_constant(&c TSRMLS_CC) == SUCCESS) {	RETURN_TRUE;} else {	RETURN_FALSE;}

php 的defined函数

if (zend_get_constant_ex(name, name_len, &c, NULL, ZEND_FETCH_CLASS_SILENT TSRMLS_CC)) {	zval_dtor(&c);	RETURN_TRUE;} else {	RETURN_FALSE;}

zend_get_constant_ex调用zend_get_constantzend_hash_find(EG(zend_constants), name, name_len+1, (void **) &c)

 php注册常量的步骤

php_cgi_startup() -> php_module_startup() ->zend_startup() -> zend_register_standard_constants()->zend_register_constant()

zend_hash_add(EG(zend_constants), name, c->name_len, (void *) c,	        sizeof(zend_constant), NULL)==FAILURE)