PHP 核心、Zend 引擎與 SAPI 模組定義的常數：
PHP_VERSION - PHP 版本字串PHP_OS - 作業系統名稱PHP_EOL - 換行符號 (PHP 4.3.10+/5.0.2+)PHP_INT_MAX - 整數最大值 (PHP 4.4.0+/5.0.5+)PHP_INT_SIZE - 整數位元組大小 (PHP 4.4.0+/5.0.5+)DEFAULT_INCLUDE_PATHPEAR_INSTALL_DIR, PEAR_EXTENSION_DIRPHP_EXTENSION_DIR, PHP_BINDIR, PHP_LIBDIRPHP_DATADIR, PHP_SYSCONFDIR, PHP_LOCALSTATEDIRPHP_CONFIG_FILE_PATH - php.ini 路徑PHP_OUTPUT_HANDLER_STARTPHP_OUTPUT_HANDLER_CONTPHP_OUTPUT_HANDLER_ENDE_ERROR, E_WARNING, E_PARSE, E_NOTICEE_CORE_ERROR, E_CORE_WARNINGE_COMPILE_ERROR, E_COMPILE_WARNINGE_USER_ERROR, E_USER_WARNING, E_USER_NOTICEE_ALL - 所有錯誤E_STRICT - 嚴格標準建議 (PHP 5.0.0+)EXTR_OVERWRITE, EXTR_SKIP, EXTR_PREFIX_SAME...SORT_ASC, SORT_DESC, SORT_REGULAR, SORT_NUMERIC, SORT_STRINGCASE_LOWER, CASE_UPPERCOUNT_NORMAL, COUNT_RECURSIVEASSERT_ACTIVE, ASSERT_CALLBACK, ASSERT_BAIL, ASSERT_WARNING, ASSERT_QUIET_EVALCONNECTION_ABORTED, CONNECTION_NORMAL, CONNECTION_TIMEOUTINI_USER, INI_PERDIR, INI_SYSTEM, INI_ALLM_E, M_LOG2E, M_LOG10E, M_LN2, M_LN10M_PI, M_PI_2, M_PI_4, M_1_PI, M_2_PIM_SQRT2, M_SQRT1_2CRYPT_SALT_LENGTH, CRYPT_STD_DES, CRYPT_EXT_DES, CRYPT_MD5, CRYPT_BLOWFISHDIRECTORY_SEPARATOR - 目錄分隔符SEEK_SET, SEEK_CUR, SEEK_END - 檔案指標定位LOCK_SH, LOCK_EX, LOCK_UN, LOCK_NB - 檔案鎖定HTML_SPECIALCHARS, HTML_ENTITIESENT_COMPAT, ENT_QUOTES, ENT_NOQUOTESINFO_GENERAL, INFO_CREDITS, INFO_CONFIGURATION, INFO_MODULES, INFO_ENVIRONMENT, INFO_VARIABLES, INFO_LICENSE, INFO_ALLSTR_PAD_LEFT, STR_PAD_RIGHT, STR_PAD_BOTHPATHINFO_DIRNAME, PATHINFO_BASENAME, PATHINFO_EXTENSIONPATH_SEPARATORLC_CTYPE, LC_NUMERIC, LC_TIME, LC_COLLATE, LC_MONETARY, LC_ALL, LC_MESSAGESABDAY_1~DAY_7, ABMON_1~MON_12INT_CURR_SYMBOL, CURRENCY_SYMBOL, MON_DECIMAL_POINT...LOG_EMERG, LOG_ALERT, LOG_CRIT, LOG_ERR, LOG_WARNING, LOG_NOTICE, LOG_INFO, LOG_DEBUGLOG_KERN, LOG_USER, LOG_MAIL, LOG_DAEMON, LOG_AUTH, LOG_SYSLOG, LOG_LPR, LOG_NEWS, LOG_UUCP, LOG_CRON, LOG_AUTHPRIV, LOG_LOCAL0~LOG_LOCAL7LOG_PID, LOG_CONS, LOG_ODELAY, LOG_NDELAY, LOG_NOWAIT, LOG_PERROR參考 __LINE__, __FILE__, __DIR__, __FUNCTION__, __CLASS__, __METHOD__, __NAMESPACE__, __COMPILER_HALT_OFFSET__ (PHP 5.1.0+)
