下列常量由此扩展定义，且仅在此扩展编译入 PHP 或在运行时动态载入时可用。
CRYPT_SALT_LENGTH
integer
CRYPT_STD_DES
integer
CRYPT_EXT_DES
integer
CRYPT_MD5
integer
CRYPT_BLOWFISH
integer
HTML_SPECIALCHARS
(integer)
HTML_ENTITIES
(integer)
ENT_COMPAT
(integer)
ENT_QUOTES
(integer)
ENT_NOQUOTES
(integer)
ENT_IGNORE
(integer)
ENT_SUBSTITUTE
(integer)
ENT_DISALLOWED
(integer)
ENT_HTML401
(integer)
ENT_XML1
(integer)
ENT_XHTML
(integer)
ENT_HTML5
(integer)
CHAR_MAX
(integer)
LC_CTYPE
(integer)
LC_NUMERIC
(integer)
LC_TIME
(integer)
LC_COLLATE
(integer)
LC_MONETARY
(integer)
LC_ALL
(integer)
LC_MESSAGES
(integer)
STR_PAD_LEFT
(integer)
STR_PAD_RIGHT
(integer)
STR_PAD_BOTH
(integer)