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<chapter xml:id="features.connection-handling" xmlns="http://docbook.org/ns/docbook">

<title>Connection handling</title>

<para>

Internally in PHP a connection status is maintained. There are 4

possible states:

<itemizedlist>

<listitem><simpara>0 - NORMAL</simpara></listitem>

<listitem><simpara>1 - ABORTED</simpara></listitem>

<listitem><simpara>2 - TIMEOUT</simpara></listitem>

<listitem><simpara>3 - ABORTED and TIMEOUT</simpara></listitem>

</itemizedlist>

</para>

<simpara>

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

users hitting their STOP button. If the PHP-imposed time limit (see

<function>set_time_limit</function>) is hit, the TIMEOUT state flag

is turned on.</simpara>

<simpara>

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 <literal>php_value ignore_user_abort</literal> Apache

&httpd.conf; directive or

with the <function>ignore_user_abort</function> 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 <function>register_shutdown_function</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 <function>connection_aborted</function>

function. This function will return &true; if the connection was

aborted.</simpara>

<simpara>

Your script can also be terminated by the built-in script timer.

The default timeout is 30 seconds. It can be changed using

the <option>max_execution_time</option> &php.ini; directive or the corresponding

<literal>php_value max_execution_time</literal> Apache &httpd.conf;

directive as well as with

the <function>set_time_limit</function> 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

<function>connection_status</function> function. This function will

return 2 if a timeout caused the shutdown function to be called.

</simpara>

<simpara>

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 <function>connection_status</function>

returns 3.

</simpara>

</chapter>

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