Chapter 20. Connection handling
Note: The following applies to 3.0.7 and later.
Internally in PHP a connection status is maintained. There
are 3 possible states:
0 - NORMAL
1 - ABORTED
2 - TIMEOUT
When a PHP script is running normally the NORMAL state,
is active. If the remote client disconnects the ABORTED
state flag is turned on. A remote client disconnect is usually
caused by the user hitting his STOP button. If the PHP-imposed
time limit (see set_time_limit()) is hit, the TIMEOUT state
flag is turned on.
You can decide whether or not you want a client disconnect
to cause your script to be aborted. Sometimes it is handy
to always have your scripts run to completion even if there
is no remote browser receiving the output. The default behaviour
is however for your script to be aborted when the remote
client disconnects. This behaviour can be set via the ignore_user_abort
php.ini directive as well as through the corresponding "php_value
ignore_user_abort" Apache .conf directive or with the
ignore_user_abort() function. If you do not tell PHP to
ignore a user abort and the user aborts, your script will
terminate. The one exception is if you have registered a
shutdown function using register_shutdown_function(). With
a shutdown function, when the remote user hits his STOP
button, the next time your script tries to output something
PHP will detect that the connection has been aborted and
the shutdown function is called. This shutdown function
will also get called at the end of your script terminating
normally, so to do something different in case of a client
disconnect you can use the connection_aborted() function.
This function will return TRUE if the connection was aborted.
Your script can also be terminated by the built-in script
timer. The default timeout is 30 seconds. It can be changed
using the max_execution_time php.ini directive or the corresponding
"php_value max_execution_time" Apache .conf directive
as well as with the set_time_limit() function. When the
timer expires the script will be aborted and as with the
above client disconnect case, if a shutdown function has
been registered it will be called. Within this shutdown
function you can check to see if a timeout caused the shutdown
function to be called by calling the connection_timeout()
function. This function will return TRUE if a timeout caused
the shutdown function to be called.
One thing to note is that both the ABORTED and the TIMEOUT
states can be active at the same time. This is possible
if you tell PHP to ignore user aborts. PHP will still note
the fact that a user may have broken the connection, but
the script will keep running. If it then hits the time limit
it will be aborted and your shutdown function, if any, will
be called. At this point you will find that connection_timeout()
and connection_aborted() return TRUE. You can also check
both states in a single call by using the connection_status().
This function returns a bitfield of the active states. So,
if both states are active it would return 3, for example.
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