接続処理

PHP 内部で、接続ステータスが保持されます。これは、次の 4 つの状態をとりえます。

0 - NORMAL
1 - ABORTED
2 - TIMEOUT
3 - ABORTED および TIMEOUT

通常 PHP が実行されている場合、NORMAL 状態がアクティブになります。リモートクライアントが接続を切った場合、ABORTED 状態フラグが有効になります。通常、リモートクライアントの接続断は、STOP ボタンを押すことにより発生します。 PHP 側の時間制限 (set_time_limit() 参照) にかかった場合、 TIMEOUT 状態フラグが有効になります。

スクリプトを終了させるためにクライアントとの接続を切断するかどうかを決めることが出来ます。時々、出力がどのリモートブラウザにも受信されない場合でも、常にスクリプトの実行完了まで実行する方が便利であることがあります。しかし、デフォルトの動作はリモートクライアントとの接続が断となった際にスクリプトの実行は破棄されます。この動作は、php.ini ディレクティブ ignore_user_abort にて設定できます。同様に同じ意味を有する Apache httpd.conf ディレクティブ php_value ignore_user_abort または ignore_user_abort() 関数にて設定することも可能です。 PHP にユーザーによる破棄を無視するように設定していない場合、ユーザーが破棄した場合、スクリプトの実行は終了します。一つの例外は、register_shutdown_function() を用いてシャットダウン関数を定義した場合です。シャットダウン関数を定義した場合、リモートユーザーが STOP ボタンを押した後、次にスクリプトが何か出力を行おうとした場合、PHP は接続が破棄されたことを検知し、シャットダウン関数がコールされます。このシャットダウン関数は、スクリプトが正常に終了した際にもコールされます。このため、クライアントが接続を切断した場合に別の動作をさせたい場合には、connection_aborted() 関数を使用することが可能です。この関数は、接続が破棄された場合に、true を返します。

スクリプトは、組み込みのスクリプトタイマーによっても終了することができます。デフォルトのタイムアウトは、30 秒です。これは、php.iniディレクティブ max_execution_time または同義の Apache httpd.conf ディレクティブ php_value max_execution_time を set_time_limit() 関数と同様に用いることにより変更することが可能です。タイマーが切れた時、スクリプトは中断されます。上記のクライアントが接続を切るケースのようにシャットダウン関数が登録されている場合、この関数がコールされます。このシャットダウン関数の中では、 connection_status() 関数のコールによりタイムアウトがシャットダウン関数のコールを生じさせるかどうかを確認することができます。この関数は、タイムアウトによりシャットダウン関数がコールされた場合に 2 を返します。

もう一つ注意すべき点は、状態 ABORTED および TIMEOUT は同時にアクティブにできるということです。これは、PHP をユーザーによる中断を無視するよう設定した場合に可能です。 PHP は、ユーザーが接続を破棄しているが、スクリプトは実行しつづけるということがある可能性があることに注意する必要があります。時間制限にかかって中断される場合、もしあればシャットダウン関数がコールされます。ここで、connection_status() は 3 を返します。

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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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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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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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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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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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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();

down

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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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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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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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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