标准常量的初始化
通过define()函数定义的模块编号都是PHP_USER_CONSTANT这表示是用户定义的常量。除此之外我们在平时使用较多的常量：如错误报告级别E_ALL, E_WARNING等常量就有点不同了。这些是PHP内置定义的常量，他们属于标准常量
在Zend引擎启动后，会执行如下的标准常量注册操作。 php_module_startup() -> zend_startup() -> zend_register_standard_constants()
1 void zend_register_standard_constants(TSRMLS_D) 2 { 3 REGISTER_MAIN_LONG_CONSTANT("E_ERROR", E_ERROR, CONST_PERSISTENT | CONST_CS); 4 REGISTER_MAIN_LONG_CONSTANT("E_RECOVERABLE_ERROR", E_RECOVERABLE_ERROR, CONST_PERSISTENT | CONST_CS); 5 REGISTER_MAIN_LONG_CONSTANT("E_WARNING", E_WARNING, CONST_PERSISTENT | CONST_CS); 6 REGISTER_MAIN_LONG_CONSTANT("E_PARSE", E_PARSE, CONST_PERSISTENT | CONST_CS); 7 REGISTER_MAIN_LONG_CONSTANT("E_NOTICE", E_NOTICE, CONST_PERSISTENT | CONST_CS); 8 REGISTER_MAIN_LONG_CONSTANT("E_STRICT", E_STRICT, CONST_PERSISTENT | CONST_CS); 9 REGISTER_MAIN_LONG_CONSTANT("E_DEPRECATED", E_DEPRECATED, CONST_PERSISTENT | CONST_CS); 10 REGISTER_MAIN_LONG_CONSTANT("E_CORE_ERROR", E_CORE_ERROR, CONST_PERSISTENT | CONST_CS); 11 REGISTER_MAIN_LONG_CONSTANT("E_CORE_WARNING", E_CORE_WARNING, CONST_PERSISTENT | CONST_CS); 12 REGISTER_MAIN_LONG_CONSTANT("E_COMPILE_ERROR", E_COMPILE_ERROR, CONST_PERSISTENT | CONST_CS); 13 REGISTER_MAIN_LONG_CONSTANT("E_COMPILE_WARNING", E_COMPILE_WARNING, CONST_PERSISTENT | CONST_CS); 14 REGISTER_MAIN_LONG_CONSTANT("E_USER_ERROR", E_USER_ERROR, CONST_PERSISTENT | CONST_CS); 15 REGISTER_MAIN_LONG_CONSTANT("E_USER_WARNING", E_USER_WARNING, CONST_PERSISTENT | CONST_CS); 16 REGISTER_MAIN_LONG_CONSTANT("E_USER_NOTICE", E_USER_NOTICE, CONST_PERSISTENT | CONST_CS); 17 REGISTER_MAIN_LONG_CONSTANT("E_USER_DEPRECATED", E_USER_DEPRECATED, CONST_PERSISTENT | CONST_CS); 18 19 REGISTER_MAIN_LONG_CONSTANT("E_ALL", E_ALL, CONST_PERSISTENT | CONST_CS); 20 21 REGISTER_MAIN_LONG_CONSTANT("DEBUG_BACKTRACE_PROVIDE_OBJECT", DEBUG_BACKTRACE_PROVIDE_OBJECT, CONST_PERSISTENT | CONST_CS); 22 REGISTER_MAIN_LONG_CONSTANT("DEBUG_BACKTRACE_IGNORE_ARGS", DEBUG_BACKTRACE_IGNORE_ARGS, CONST_PERSISTENT | CONST_CS); 23 /* true/false constants */ 24 { 25 zend_constant c; 26 27 c.flags = CONST_PERSISTENT | CONST_CT_SUBST; 28 c.module_number = 0; 29 30 c.name = zend_strndup(ZEND_STRL("TRUE")); 31 c.name_len = sizeof("TRUE"); 32 c.value.value.lval = 1; 33 c.value.type = IS_BOOL; 34 zend_register_constant(&c TSRMLS_CC); 35 36 c.name = zend_strndup(ZEND_STRL("FALSE")); 37 c.name_len = sizeof("FALSE"); 38 c.value.value.lval = 0; 39 c.value.type = IS_BOOL; 40 zend_register_constant(&c TSRMLS_CC); 41 42 c.name = zend_strndup(ZEND_STRL("NULL")); 43 c.name_len = sizeof("NULL"); 44 c.value.type = IS_NULL; 45 zend_register_constant(&c TSRMLS_CC); 46 47 c.flags = CONST_PERSISTENT; 48 49 c.name = zend_strndup(ZEND_STRL("ZEND_THREAD_SAFE")); 50 c.name_len = sizeof("ZEND_THREAD_SAFE"); 51 c.value.value.lval = ZTS_V; 52 c.value.type = IS_BOOL; 53 zend_register_constant(&c TSRMLS_CC); 54 55 c.name = zend_strndup(ZEND_STRL("ZEND_DEBUG_BUILD")); 56 c.name_len = sizeof("ZEND_DEBUG_BUILD"); 57 c.value.value.lval = ZEND_DEBUG; 58 c.value.type = IS_BOOL; 59 zend_register_constant(&c TSRMLS_CC); 60 } 61 }
定义了一堆标准常量,REGISTER_MAIN_LONG_CONSTANT()是一个宏，用于注册一个长整形数字的常量，因为C是强类型语言，不同类型的数据等分别处理。在 zend_constants.c和zend_constants.h中有这些宏的声明和定义