SESSION在不同页面传递时丢失，不过COOKIE可以用。这是为什么？
这是PHP.INI中关于SESSION 的内容：
; Handler used to store/retrieve data.
session.save_handler = files; Argument passed to save_handler. In the case of files, this is the path
; where data files are stored. Note: Windows users have to change this
; variable in order to use PHP's session functions.
;
; As of PHP 4.0.1, you can define the path as:
;
; session.save_path = "N;/path"
;
; where N is an integer. Instead of storing all the session files in
; /path, what this will do is use subdirectories N-levels deep, and
; store the session data in those directories. This is useful if you
; or your OS have problems with lots of files in one directory, and is
; a more efficient layout for servers that handle lots of sessions.
;
; NOTE 1: PHP will not create this directory structure automatically.
; You can use the script in the ext/session dir for that purpose.
; NOTE 2: See the section on garbage collection below if you choose to
; use subdirectories for session storage
;
; The file storage module creates files using mode 600 by default.
; You can change that by using
;
; session.save_path = "N;MODE;/path"
;
; where MODE is the octal representation of the mode. Note that this
; does not overwrite the process's umask.
;session.save_path = "/tmp"; Whether to use cookies.
session.use_cookies = 1;session.cookie_secure = ; This option enables administrators to make their users invulnerable to
; attacks which involve passing session ids in URLs; defaults to 0.
; session.use_only_cookies = 1; Name of the session (used as cookie name).
session.name = PHPSESSID; Initialize session on request startup.
session.auto_start = 0; Lifetime in seconds of cookie or, if 0, until browser is restarted.
session.cookie_lifetime = 0; The path for which the cookie is valid.
session.cookie_path = /; The domain for which the cookie is valid.
session.cookie_domain =; Whether or not to add the httpOnly flag to the cookie, which makes it inaccessible to browser scripting languages such as JavaScript.
session.cookie_httponly = ; Handler used to serialize data. php is the standard serializer of PHP.
session.serialize_handler = php; Define the probability that the 'garbage collection' process is started
; on every session initialization.
; The probability is calculated by using gc_probability/gc_divisor,
; e.g. 1/100 means there is a 1% chance that the GC process starts
; on each request.session.gc_probability = 1
session.gc_divisor = 100; After this number of seconds, stored data will be seen as 'garbage' and
; cleaned up by the garbage collection process.
session.gc_maxlifetime = 1440; NOTE: If you are using the subdirectory option for storing session files
; (see session.save_path above), then garbage collection does *not*
; happen automatically. You will need to do your own garbage
; collection through a shell script, cron entry, or some other method.
; For example, the following script would is the equivalent of
; setting session.gc_maxlifetime to 1440 (1440 seconds = 24 minutes):
; cd /path/to/sessions; find -cmin +24 | xargs rm; PHP 4.2 and less have an undocumented feature/bug that allows you to
; to initialize a session variable in the global scope, albeit register_globals
; is disabled. PHP 4.3 and later will warn you, if this feature is used.
; You can disable the feature and the warning separately. At this time,
; the warning is only displayed, if bug_compat_42 is enabled.session.bug_compat_42 = 1
session.bug_compat_warn = 1; Check HTTP Referer to invalidate externally stored URLs containing ids.
; HTTP_REFERER has to contain this substring for the session to be
; considered as valid.
session.referer_check =; How many bytes to read from the file.
session.entropy_length = 0; Specified here to create the session id.
session.entropy_file =;session.entropy_length = 16;session.entropy_file = /dev/urandom; Set to {nocache,private,public,} to determine HTTP caching aspects
; or leave this empty to avoid sending anti-caching headers.
session.cache_limiter = nocache; Document expires after n minutes.
session.cache_expire = 180; trans sid support is disabled by default.
; Use of trans sid may risk your users security.
; Use this option with caution.
; - User may send URL contains active session ID
; to other person via. email/irc/etc.
; - URL that contains active session ID may be stored
; in publically accessible computer.
; - User may access your site with the same session ID
; always using URL stored in browser's history or books.
session.use_trans_sid = 0; Select a hash function
; 0: MD5 (128 bits)
; 1: SHA-1 (160 bits)
session.hash_function = 0; Define how many bits are stored in each character when converting
; the binary hash data to something readable.
;
; 4 bits: 0-9, a-f
; 5 bits: 0-9, a-v
; 6 bits: 0-9, a-z, A-Z, "-", ","
session.hash_bits_per_character = 4
这是PHP.INI中关于SESSION 的内容：
; Handler used to store/retrieve data.
session.save_handler = files; Argument passed to save_handler. In the case of files, this is the path
; where data files are stored. Note: Windows users have to change this
; variable in order to use PHP's session functions.
;
; As of PHP 4.0.1, you can define the path as:
;
; session.save_path = "N;/path"
;
; where N is an integer. Instead of storing all the session files in
; /path, what this will do is use subdirectories N-levels deep, and
; store the session data in those directories. This is useful if you
; or your OS have problems with lots of files in one directory, and is
; a more efficient layout for servers that handle lots of sessions.
;
; NOTE 1: PHP will not create this directory structure automatically.
; You can use the script in the ext/session dir for that purpose.
; NOTE 2: See the section on garbage collection below if you choose to
; use subdirectories for session storage
;
; The file storage module creates files using mode 600 by default.
; You can change that by using
;
; session.save_path = "N;MODE;/path"
;
; where MODE is the octal representation of the mode. Note that this
; does not overwrite the process's umask.
;session.save_path = "/tmp"; Whether to use cookies.
session.use_cookies = 1;session.cookie_secure = ; This option enables administrators to make their users invulnerable to
; attacks which involve passing session ids in URLs; defaults to 0.
; session.use_only_cookies = 1; Name of the session (used as cookie name).
session.name = PHPSESSID; Initialize session on request startup.
session.auto_start = 0; Lifetime in seconds of cookie or, if 0, until browser is restarted.
session.cookie_lifetime = 0; The path for which the cookie is valid.
session.cookie_path = /; The domain for which the cookie is valid.
session.cookie_domain =; Whether or not to add the httpOnly flag to the cookie, which makes it inaccessible to browser scripting languages such as JavaScript.
session.cookie_httponly = ; Handler used to serialize data. php is the standard serializer of PHP.
session.serialize_handler = php; Define the probability that the 'garbage collection' process is started
; on every session initialization.
; The probability is calculated by using gc_probability/gc_divisor,
; e.g. 1/100 means there is a 1% chance that the GC process starts
; on each request.session.gc_probability = 1
session.gc_divisor = 100; After this number of seconds, stored data will be seen as 'garbage' and
; cleaned up by the garbage collection process.
session.gc_maxlifetime = 1440; NOTE: If you are using the subdirectory option for storing session files
; (see session.save_path above), then garbage collection does *not*
; happen automatically. You will need to do your own garbage
; collection through a shell script, cron entry, or some other method.
; For example, the following script would is the equivalent of
; setting session.gc_maxlifetime to 1440 (1440 seconds = 24 minutes):
; cd /path/to/sessions; find -cmin +24 | xargs rm; PHP 4.2 and less have an undocumented feature/bug that allows you to
; to initialize a session variable in the global scope, albeit register_globals
; is disabled. PHP 4.3 and later will warn you, if this feature is used.
; You can disable the feature and the warning separately. At this time,
; the warning is only displayed, if bug_compat_42 is enabled.session.bug_compat_42 = 1
session.bug_compat_warn = 1; Check HTTP Referer to invalidate externally stored URLs containing ids.
; HTTP_REFERER has to contain this substring for the session to be
; considered as valid.
session.referer_check =; How many bytes to read from the file.
session.entropy_length = 0; Specified here to create the session id.
session.entropy_file =;session.entropy_length = 16;session.entropy_file = /dev/urandom; Set to {nocache,private,public,} to determine HTTP caching aspects
; or leave this empty to avoid sending anti-caching headers.
session.cache_limiter = nocache; Document expires after n minutes.
session.cache_expire = 180; trans sid support is disabled by default.
; Use of trans sid may risk your users security.
; Use this option with caution.
; - User may send URL contains active session ID
; to other person via. email/irc/etc.
; - URL that contains active session ID may be stored
; in publically accessible computer.
; - User may access your site with the same session ID
; always using URL stored in browser's history or books.
session.use_trans_sid = 0; Select a hash function
; 0: MD5 (128 bits)
; 1: SHA-1 (160 bits)
session.hash_function = 0; Define how many bits are stored in each character when converting
; the binary hash data to something readable.
;
; 4 bits: 0-9, a-f
; 5 bits: 0-9, a-v
; 6 bits: 0-9, a-z, A-Z, "-", ","
session.hash_bits_per_character = 4
还有session本来就会存在时间超时的情况，如果你程序里没有把session清空的话，那就设置一下过期时间吧
session 的默认时间为：1440s即24分
以下是设置时间的方法：
＜?php
session_start();
// 保存一天
$lifeTime = 24 * 3600;
setcookie(session_name(), session_id(), time() + $lifeTime, "/");
?＞