A trick to detecting if a connection is closed without having to send data that will otherwise corrupt the stream of data (like a binary file) you can use a combination of chunking the data on HTTP/1.1 by sending a "0" ("zero") as a leading chunk size without anything else.
*NOTE* it's important to note that it's not a good idea to check the stream more then once every few seconds. By doing this you are potentially increasing the data sent to the user with no gain to the user.
A good reason to do it this way is if you are generating a report that takes a long time to run and takes a lot of server resources. This would allow the server to detect if a user canceled the download and do any cleanup without corrupting the file file being download.
Here is an example:
<?php
ignore_user_abort(true);
header('Transfer-Encoding:chunked');
ob_flush();
flush();
$start = microtime(true);
$i = 0;
// Use this function to echo anything to the browser.
function vPrint($data){
if(strlen($data))
echo dechex(strlen($data)), "\r\n", $data, "\r\n";
ob_flush();
flush();
}
// You MUST execute this function after you are done streaming information to the browser.
function endPacket(){
echo "0\r\n\r\n";
ob_flush();
flush();
}
do{
echo "0";
ob_flush();
flush();
if(connection_aborted()){
// This happens when connection is closed
file_put_contents('/tmp/test.tmp', sprintf("Conn Closed\nTime spent with connection open: %01.5f sec\nLoop itterations: %s\n\n", microtime(true) - $start, $i), FILE_APPEND);
endPacket();
exit;
}
usleep(50000);
vPrint("I get echo'ed every itteration (every .5 second)<br />\n");
}while($i++ < 200);
endPacket();
?>
connection_aborted
(PHP 4, PHP 5, PHP 7, PHP 8)
connection_aborted — Check whether client disconnected
Parameters
This function has no parameters.
Return Values
Returns 1 if client disconnected, 0 otherwise.
See Also
- connection_status() - Returns connection status bitfield
- ignore_user_abort() - Set whether a client disconnect should abort script execution
- Connection Handling for a complete description of connection handling in PHP.
add a note
User Contributed Notes 8 notes
nathanb at php dot net ¶
11 years ago
Rupak Bajgain ¶
1 year ago
One trick i used uas to send values in comment to get long pooling with disconnect check
Like for json:
Send 0 and flush before connection aborted.
Eg. {"x":"000000
And after result is ready send ", and json after removing 1st {
So it looks like
{"x":"00000000000","y":"result","z":"result2"}
Luciano ¶
14 years ago
In order to detect a disconnection inside the script we need to flush the buffer (it is only when the the server tries to send the buffer content that it will see that the connection is broken).
Thus we need to use the ob_implicit_flush() function to flush automatically the buffer
This is an example of a disconnection detection :
<?php
// enables the automatic flush
ob_implicit_flush();
function verifyCommunication() {
$status = (connection_aborted()?"not ":"") ."sent";
persistCommunication(new Communication($status));
}
// we will check the communication state when the script finished
register_shutdown_function(verifyCommunication);
echo "blabla";
// this sleep is used to have time to break the connection on the client side
sleep(10);
echo"tata";
?>
I use such a process to cancel a request if the client didn't get the acknowledgement because he will redo his request...
sivann at gmail dot com ¶
8 years ago
I have failed to get accurate results from this even with echo, flush(), and other buffer manipulation trickery. The following function detects connection status from the OS netstat(1) in linux, even without echoing anything. You may need to alter the parsing for windows or older versions of netstat. It calls an external command so it consume some resources, use it with care e.g. you can call it every some seconds while waiting for long-poll requests. Not tested with ipv6.
//returns connection status (ESTABLISHED, TIME_WAIT, etc) or NOT_FOUND
function getConnectionStatus() {
$remote_ip = $_SERVER['REMOTE_ADDR']?:($_SERVER['HTTP_X_FORWARDED_FOR']?:$_SERVER['HTTP_CLIENT_IP']);
$remote_port=$_SERVER['REMOTE_PORT'];
$cmd="netstat -tn | fgrep ' $remote_ip:$remote_port '";
$pfp=popen($cmd,"r");
if(!$pfp) {
error_log ("getConnectionStatus: $cmd");
}
$buf = fgets($pfp, 1024);
pclose($pfp);
$buf=preg_replace('!\s+!', ' ', $buf); //remove multiple spaces
$buf=trim($buf);
$buf_r=explode(" ",$buf);
if (count($buf_r)) {
$state=$buf_r[count($buf_r)-1];
return trim($state);
}
return "NOTFOUND";
}
//check for it:
if (getConnectionStatus() != "ESTABLISHED") { ...}
jeff1326 at hotmail dot com ¶
9 years ago
From ignore_user_abort function :
PHP will not detect that the user has aborted the connection until an attempt is made to send information to the client. Simply using an echo statement does not guarantee that information is sent, see flush().
This rule seems to apply here too.
jamest344 at gmail dot com ¶
6 years ago
Declaration: I'm a novice.
The action on client connection loss which I wanted occurred upon browser or tab closure but not upon network link severance. This was remedied by nobbling apache2's mod_deflate. Other conf settings I changed may also be important (timeout?). Thus at the bottom of my page.html I have:
<script>
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
}
};
xhttp.open("GET", "Caller.php", true);
xhttp.send();
</script>
Then in Caller.php I have:
<?php
ignore_user_abort(TRUE);
Header('Location: monitor.php');
?>
And in monitor.php:
<?php
ignore_user_abort(TRUE);
set_time_limit(0);
echo connection_status();
while(1)
{
echo "something - anything - to go here - need a good few lines of it";
ob_flush();
flush();
sleep(1);
if(connection_status()!=0)
{
break;
}
}
shell_exec("DESIRED ACTION HERE");
?>
phpcoder at cyberpimp dot techlab dot info ¶
17 years ago
Although the documentation indicates it returns an int, I found comparing the return value with numeric values does not seem to work.
Example (does not work):
<?php
if (connection_aborted()==1) {
fwrite($filehandle, 'aborted!');
}
?>
You're better off just assuming it returns boolean
Example (does work):
<?php
if (connection_aborted()) {
fwrite($filehandle, 'aborted!');
}
?>
rickyale at ig dot com dot br ¶
15 years ago
(connection_aborted not working)
I had this problem years ago, now the problem came back after upgrading php... i tried everything i found and in the end the function ob_end_flush(); on top of script as post in php bug track solved the problem. Im using windows 7 x64 / php 5.2.4 / apache 2.2.14 (win32)
try adding ob_end_flush(); on top of you script.
i read something about this but can't remember where, it was related to a bug or something.
hope this help.
