접속 다루기

PHP는 내부적으로 접속 상태를 관리합니다. 3가지 상태가 존재합니다:

0 - NORMAL
1 - ABORTED
2 - TIMEOUT

PHP 스크립트가 정상적으로 작동하고 있으면, NORMAL 상태가 활성화됩니다. 원격 클라이언트가 접속을 끊으면 ABORTED 상태 플래그가 켜집니다. 원격 클라이언트의 접속 차단은 보통 사용자가 중지 버튼을 누르는 경우입니다. PHP 내장 시간 제한(set_time_limit())에 걸리면, TIMEOUT 상태 플래그가 켜집니다.

클라이언트 접속 차단으로 인해 스크립트를 중단할 지 여부를 결정할 수 있습니다. 때때로 원격 브라우저가 출력을 받아들이지 않더라도 스크립트가 동작을 마쳐야 할 수 있습니다. 기본 동작은 원격 클라이언트 접속 차단 시에 스크립트를 중단합니다. 이 동작은 php.ini에서 ignore_user_abort 지시어나, , 아파치 .conf php_value ignore_user_abort 지시어, ignore_user_abort() 함수로 설정할 수 있습니다. PHP에 사용자 중단을 무시하도록 하지 않고 사용자가 중단하면, 스크립트는 종료됩니다. 한가지 예외는 register_shutdown_function()을 사용하여 종료 함수를 등록했을 경우입니다. 종료 함수가 있으면 사용자가 중단 버튼을 눌렀을 때, 스크립트에서 무언가를 출력하려 해서 PHP가 접속이 중단되었음을 알게 되었을 경우 종료 함수가 호출됩니다. 이 종료 함수는 정상적으로 스크립트 마지막에 종료될 때도 호출되므로, 클라이언트 접속 차단시 다른 동작을 하려면 connection_aborted() 함수를 이용할 수 있습니다. 이 함수는 접속이 취소되었을 때 TRUE를 반환합니다.

스크립트는 내장 스크립트 타이머에 의해 종료될 수도 있습니다. 기본 시간 제한은 30초입니다. 이는 php.ini max_execution_time 지시어나, 아파치 .conf php_value max_execution_time 지시어, set_time_limit() 함수로 바꿀 수 있습니다. 타이머가 초과되면 스크립트는 중단되고, 위의 클라이언트 접속 차단의 경우와 마찬가지로 종료함수가 있으면 호출됩니다. 종료 함수에서 connection_status() 함수를 호출하여 시간 초과가 종료 함수 호출을 유발하였는지 확인할 수 있습니다. 이 함수는 시간 초과가 원인으로 종료 함수를 호출하였을 때 2를 반환합니다.

ABORTED와 TIMEOUT 상태가 동시에 일어날 수 있는 점에 주의해야 합니다. 이는 PHP에 사용자 중단을 무시하도록 했을 때 일어날 수 있습니다. PHP는 사용자가 접속을 끊었음을 기록하지만, 스크립트는 계속 실행됩니다. 그리고 시간 제한에 도달하여 취소되면 종료 함수가 존재할 경우 호출됩니다. 이 경우 connection_status()가 3을 반환합니다.

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User Contributed Notes 12 notes

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tom lgold2003 at gmail dot com ¶

14 years ago


hey, thanks to arr1, and it is very useful for me, when I need to return to the user fast and then do something else.

When using the codes, it nearly drive me mad and I found another thing that may affect the codes:

Content-Encoding: gzip

This is because the zlib is on and the content will be compressed. But this will not output the buffer until all output is over.

So, it may need to send the header to prevent this problem.

now, the code becomes:

<?php
ob_end_clean();
header("Connection: close\r\n");
header("Content-Encoding: none\r\n");
ignore_user_abort(true); // optional
ob_start();
echo ('Text user will see');
$size = ob_get_length();
header("Content-Length: $size");
ob_end_flush();     // Strange behaviour, will not work
flush();            // Unless both are called !
ob_end_clean();

//do processing here
sleep(5);

echo('Text user will never see');
//do some processing
?>

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arr1 at hotmail dot co dot uk ¶

17 years ago


Closing the users browser connection whilst keeping your php script running has been an issue since 4.1, when the behaviour of register_shutdown_function() was modified so that it would not automatically close the users connection.

sts at mail dot xubion dot hu
Posted the original solution:

<?php
header("Connection: close");
ob_start();
phpinfo();
$size=ob_get_length();
header("Content-Length: $size");
ob_end_flush();
flush();
sleep(13);
error_log("do something in the background");
?>

Which works fine until you substitute phpinfo() for 
echo ('text I want user to see'); in which case the headers are never sent!

The solution is to explicitly turn off output buffering and clear the buffer prior to sending your header information.

example:

<?php
 ob_end_clean();
 header("Connection: close");
 ignore_user_abort(); // optional
 ob_start();
 echo ('Text the user will see');
 $size = ob_get_length();
 header("Content-Length: $size");
 ob_end_flush(); // Strange behaviour, will not work
 flush();            // Unless both are called !
 // Do processing here 
 sleep(30);
 echo('Text user will never see');
?>
 
Just spent 3 hours trying to figure this one out, hope it helps someone :)

Tested in:
IE 7.5730.11
Mozilla Firefox 1.81

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mheumann at comciencia dot cl ¶

10 years ago


I had a lot of problems getting a redirect to work, after which my script was intended to keep working in the background. The redirect to another page of my site simply would only work once the original page had finished processing.

I finally found out what was wrong:
The session only gets closed by PHP at the very end of the script, and since access to the session data is locked to prevent more than one page writing to it simultaneously, the new page cannot load until the original processing has finished.

Solution:
Close the session manually when redirecting using session_write_close():

<?php
ignore_user_abort(true);
set_time_limit(0);

$strURL = "PUT YOUR REDIRCT HERE";
header("Location: $strURL", true);
header("Connection: close", true);
header("Content-Encoding: none\r\n");
header("Content-Length: 0", true);

flush();
ob_flush();

session_write_close();

// Continue processing...

sleep(100);
exit;
?>

But careful:
Make sure that your script doesn't write to the session after session_write_close(), i.e. in your background processing code.  That won't work.  Also avoid reading, remember, the next script may already have modified the data.

So try to read out the data you need prior to redirecting.

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a1n2ton at gmail dot com ¶

14 years ago


PHP changes directory on connection abort so code like this will not do what you want:

<?php
function abort()
{
     if(connection_aborted())
           unlink('file.ini');
}
register_shutdown_function('abort');
?>

actually it will delete file in apaches's root dir so if you want to unlink file in your script's dir on abort or write to it you have to store directory
<?php
function abort()
{
     global $dsd;
     if(connection_aborted())
           unlink($dsd.'/file.ini');
}
register_shutdown_function('abort');
$dsd=getcwd();
?>

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Lee ¶

19 years ago


The point mentioned in the last comment isn't always the case.

If a user's connection is lost half way through an order processing script is confirming a user's credit card/adding them to a DB, etc (due to their ISP going down, network trouble... whatever) and your script tries to send back output (such as, "pre-processing order" or any other type of confirmation), then your script will abort -- and this could cause problems for your process.

I have an order script that adds data to a InnoDB database (through MySQL) and only commits the transactions upon successful completion. Without ignore_user_abort(), I have had times when a user's connection dropped during the processing phase... and their card was charged, but they weren't added to my local DB.

So, it's always safe to ignore any aborts if you are processing sensitive transactions that should go ahead, whether your user is "watching" on the other end or not.

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Anonymous ¶

16 years ago


in regards of posting from:
arr1 at hotmail dot co dot uk

if you use/write sessions you need to do this before:
(otherwise it does not work)

session_write_close();

and if wanted:

ignore_user_abort(TRUE);
instead of ignore_user_abort();

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Ilya Penyaev ¶

11 years ago


I was quite stuck when trying to make my script redirect the client to another URL and then continue processing. The reason was php-fpm. All possible buffer flushes did not work, unless I called fastcgi_finish_request();

For example:

<?php
    // redirecting...
    ignore_user_abort(true);
    header("Location: ".$redirectUrl, true);
    header("Connection: close", true);
    header("Content-Length: 0", true);
    ob_end_flush();
    flush();
    fastcgi_finish_request(); // important when using php-fpm!
    
    sleep (5); // User won't feel this sleep because he'll already be away
    
    // do some work after user has been redirected
?>

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pulstar at mail dot com ¶

20 years ago


These functions are very useful for example if you need to control when a visitor in your website place an order and you need to check if he/she didn't clicked the submit button twice or cancelled the submit just after have clicked the submit button. 
If your visitor click the stop button just after have submitted it, your script may stop in the middle of the process of registering the products and do not finish the list, generating inconsistency in your database.
With the ignore_user_abort() function you can make your script finish everything fine and after you can check with register_shutdown_function() and connection_aborted() if the visitor cancelled the submission or lost his/her connection. If he/she did, you can set the order as not confirmed and when the visitor came back, you can present the old order again.
To prevent a double click of the submit button, you can disable it with javascript or in your script you can set a flag for that order, which will be recorded into the database. Before accept a new submission, the script will check if the same order was not placed before and reject it. This will work fine, as the script have finished the job before.
Note that if you use ob_start("callback_function") in the begin of your script, you can specify a callback function that will act like the shutdown function when our script ends and also will let you to work on the generated page before send it to the visitor.

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Anonymous ¶

12 years ago


This simple function outputs a string and closes the connection. It considers compression using "ob_gzhandler"



It took me a little while to put this all together, mostly because setting the encoding to none, as some people noted here, didn't work.



<?php

function outputStringAndCloseConnection2($stringToOutput)

{    

    set_time_limit(0);

    ignore_user_abort(true);    

    // buffer all upcoming output - make sure we care about compression:

    if(!ob_start("ob_gzhandler"))

        ob_start();         

    echo $stringToOutput;    

    // get the size of the output

    $size = ob_get_length();    

    // send headers to tell the browser to close the connection    

    header("Content-Length: $size");

    header('Connection: close');    

    // flush all output

    ob_end_flush();

    ob_flush();

    flush();    

    // close current session

    if (session_id()) session_write_close();

}

?>

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Marco ¶

7 years ago


The CONNECTION_XXX constants that are not listed here for some reason are:

0 = CONNECTION_NORMAL
1 = CONNECTION_ABORTED
2 = CONNECTION_TIMEOUT
3 = CONNECTION_ABORTED & CONNECTION_TIMEOUT

Number 3 is effectively tested like this:
if (CONNECTION_ABORTED & CONNECTION_TIMEOUT)
    echo 'Connection both aborted and timed out';

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-5

Jean Charles MAMMANA ¶

16 years ago


connection_status() return ABORTED state ONLY if the client disconnects gracefully (with STOP button). In this case the browser send the RST TCP packet that notify PHP the connection is closed.
But.... If the connection is stopped by networs troubles (wifi link down by exemple) the script doesn't know that the client is disconnected :(

I've tried to use fopen("php://output") with stream_select() on writting to detect write locks (due to full buffer) but php give me this error : "cannot represent a stream of type Output as a select()able descriptor"

So I don't know how to detect correctly network trouble connection...

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-45

robert at go dot rw ¶

8 years ago


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/*
 * Anti-Pattern
 */
 
# Connect
mysql_connect('localhost', 'username', 'password') or die('Could not connect: ' . mysql_error());
 
# Choose a database
mysql_select_db('someDatabase') or die('Could not select database');
 
# Perform database query
$query = "SELECT * from someTable";
$result = mysql_query($query) or die('Query failed: ' . mysql_error());
 
# Filter through rows and echo desired information
while ($row = mysql_fetch_object($result)) {
    echo $row->name;
}

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