php--得到我们开始使用php前的一些参数：变量 / 常量 / 模块 / 函数 / 类
1,array get_defined_vars ( void )获取由所有已定义变量所组成的数组(包括环境变量、服务器变量和用户定义的变量。)
2,array get_defined_functions ( void ) 获取所有已经定义的函数
3,array get_loaded_extensions ([ bool $zend_extensions = false ] )返回了 PHP 解析器里所有编译并加载的模块名。
参数默认是false，返回（普通扩展和zend扩展），true时只返回zend扩展。
4，array get_extension_funcs ( string $module_name )返回指定模块所有可用的函数
立即学习“PHP免费学习笔记（深入）”；
5，array get_defined_constants ([ bool $categorize = false ] )返回所有常量的关联数组，键是常量名，值是常量值
6，array get_declared_classes ( void )获取由已定义类的名字所组成的数组
7，get_included_files() / get_require_files() 返回所有被 include、 include_once、 require 和 require_once 的文件名，组成数组，第一个是本文件名。
看一下，discuz！3.x的forum.php载入了多少文件：
Array( [0] => D:\webserver\www\Discuz_X3.1\forum.php [1] => D:\webserver\www\Discuz_X3.1\source\class\class_core.php [2] => D:\webserver\www\Discuz_X3.1\source\class\discuz\discuz_application.php [3] => D:\webserver\www\Discuz_X3.1\source\class\discuz\discuz_base.php [4] => D:\webserver\www\Discuz_X3.1\source\function\function_core.php [5] => D:\webserver\www\Discuz_X3.1\config\config_global.php [6] => D:\webserver\www\Discuz_X3.1\source\class\discuz\discuz_database.php [7] => D:\webserver\www\Discuz_X3.1\source\function\function_forum.php [8] => D:\webserver\www\Discuz_X3.1\source\class\db\db_driver_mysql.php [9] => D:\webserver\www\Discuz_X3.1\source\class\table\table_common_syscache.php [10] => D:\webserver\www\Discuz_X3.1\source\class\discuz\discuz_table.php [11] => D:\webserver\www\Discuz_X3.1\source\class\discuz\discuz_memory.php [12] => D:\webserver\www\Discuz_X3.1\source\class\table\table_common_member.php [13] => D:\webserver\www\Discuz_X3.1\source\class\discuz\discuz_table_archive.php [14] => D:\webserver\www\Discuz_X3.1\source\class\discuz\discuz_session.php [15] => D:\webserver\www\Discuz_X3.1\source\class\table\table_common_session.php [16] => D:\webserver\www\Discuz_X3.1\source\class\discuz\discuz_cron.php [17] => D:\webserver\www\Discuz_X3.1\source\class\table\table_common_cron.php [18] => D:\webserver\www\Discuz_X3.1\source\class\discuz\discuz_process.php [19] => D:\webserver\www\Discuz_X3.1\source\class\table\table_common_process.php [20] => D:\webserver\www\Discuz_X3.1\source\include\cron\cron_follow_daily.php [21] => D:\webserver\www\Discuz_X3.1\source\class\table\table_home_follow_feed.php [22] => D:\webserver\www\Discuz_X3.1\source\class\helper\helper_util.php [23] => D:\webserver\www\Discuz_X3.1\source\language\lang_core.php [24] => D:\webserver\www\Discuz_X3.1\source\plugin\mobile\mobile.class.php)载入了这么多还真吓人。
总结，php在我们使用之前已经有这么多参数，有点小惊讶，特别是有一百多个类：
Array( [0] => stdClass [1] => Exception [2] => ErrorException [3] => COMPersistHelper [4] => com_exception [5] => com_safearray_proxy [6] => variant [7] => com [8] => dotnet [9] => ReflectionException [10] => Reflection [11] => ReflectionFunctionAbstract [12] => ReflectionFunction [13] => ReflectionParameter [14] => ReflectionMethod [15] => ReflectionClass [16] => ReflectionObject [17] => ReflectionProperty [18] => ReflectionExtension [19] => DateTime [20] => DateTimeZone [21] => LibXMLError [22] => __PHP_Incomplete_Class [23] => php_user_filter [24] => Directory [25] => SimpleXMLElement [26] => DOMException [27] => DOMStringList [28] => DOMNameList [29] => DOMImplementationList [30] => DOMImplementationSource [31] => DOMImplementation [32] => DOMNode [33] => DOMNameSpaceNode [34] => DOMDocumentFragment [35] => DOMDocument [36] => DOMNodeList [37] => DOMNamedNodeMap [38] => DOMCharacterData [39] => DOMAttr [40] => DOMElement [41] => DOMText [42] => DOMComment [43] => DOMTypeinfo [44] => DOMUserDataHandler [45] => DOMDomError [46] => DOMErrorHandler [47] => DOMLocator [48] => DOMConfiguration [49] => DOMCdataSection [50] => DOMDocumentType [51] => DOMNotation [52] => DOMEntity [53] => DOMEntityReference [54] => DOMProcessingInstruction [55] => DOMStringExtend [56] => DOMXPath [57] => RecursiveIteratorIterator [58] => IteratorIterator [59] => FilterIterator [60] => RecursiveFilterIterator [61] => ParentIterator [62] => LimitIterator [63] => CachingIterator [64] => RecursiveCachingIterator [65] => NoRewindIterator [66] => AppendIterator [67] => InfiniteIterator [68] => RegexIterator [69] => RecursiveRegexIterator [70] => EmptyIterator [71] => ArrayObject [72] => ArrayIterator [73] => RecursiveArrayIterator [74] => SplFileInfo [75] => DirectoryIterator [76] => RecursiveDirectoryIterator [77] => SplFileObject [78] => SplTempFileObject [79] => SimpleXMLIterator [80] => LogicException [81] => BadFunctionCallException [82] => BadMethodCallException [83] => DomainException [84] => InvalidArgumentException [85] => LengthException [86] => OutOfRangeException [87] => RuntimeException [88] => OutOfBoundsException [89] => OverflowException [90] => RangeException [91] => UnderflowException [92] => UnexpectedValueException [93] => SplObjectStorage [94] => XMLReader [95] => XMLWriter [96] => mysqli_sql_exception [97] => mysqli_driver [98] => mysqli [99] => mysqli_warning [100] => mysqli_result [101] => mysqli_stmt [102] => PDOException [103] => PDO [104] => PDOStatement [105] => PDORow)
