I'm new to Server Side Events and started some tests with PHP on the server side and Python on the client side using the sseclient library.
Using a very basic PHP script, based on the w3schools tutorial I can see the data being received in Python:
<?php
header('Content-Type: text/event-stream');
header('Cache-Control: no-cache');
function sendMsg($id, $msg) {
echo "id: $id" . PHP_EOL;
echo "data: $msg" . PHP_EOL;
echo PHP_EOL;
ob_flush();
flush();
}
$time = date('r');
// echo "data: The server time is: {$time}\n\n";
// flush();
sendMsg(time(),"The server time is: {$time}\n\n");
?>
and in Python:
#!/usr/bin/env python
from sseclient import SSEClient
messages = SSEClient('http://pathto/myscript.php')
for msg in messages:
print msg
As a second step I've tried sending data read from an array stored in the $_SESSION variable. This seems to work when I connect to the SSE stream from javascript in the browser, but it doesn't work and I'm not sure why.
Here's my basic PHP script:
<?php
session_start();
header('Content-Type: text/event-stream');
header('Cache-Control: no-cache');
function sendMsg($id, $msg) {
echo "id: $id" . PHP_EOL;
echo "data: $msg" . PHP_EOL;
echo PHP_EOL;
ob_flush();
flush();
}
// check for session data
if (isset($_SESSION["data"])){
#as long there are elements in the data array, stream one at a time, clearing the array (FIFO)
while(count($_SESSION["data"]) > 0){
$serverTime = time();
$data = array_shift($_SESSION["data"]);
sendMsg($serverTime,$data);
}
}
?>
and the Python script is the same.
Why isn't the sseclient Python script picking up the events from the above PHP script (while a basic JS one does) ?
The PHP session variable is sent as a cookie; if you view your JavaScript version with Firebug (or equivalent) you should see the cookie being sent to the SSE server script.
So you'll need to set up a session for the Python script, and have it send that in a cookie too.
You could confirm this guess by adding some error handling to your PHP script:
...
if (isset($_SESSION["data"])){
//current code here
}else{
sendMsg(time(), "Error: no session");
}
I am currently working on a chat that uses Server-Sent Events to receive the messages. However, I am running into a problem. The server-sent event never connects and stays at pending because the page doesn't load.
For example:
<?php
while(true) {
echo "data: This is the message.";
sleep(3);
ob_flush();
flush();
}
?>
I expect that every 3 seconds, "data: This is the message." will be outputted. Instead, the page just doesn't load. However, I need this behavior for server-sent events. Is there a way to fix this?
Edit:
Full Code:
<?php
session_start();
require "connect.php";
require "user.php";
session_write_close();
echo $data["number"];
header("Content-Type: text/event-stream\n\n");
header('Cache-Control: no-cache');
set_time_limit(1200);
$store = new StdClass(); // STORE LATEST MESSAGES TO COMPARE TO NEW ONES
$ms = 200; // REFRESH TIMING (in ms)
$go = true; // MESSAGE CHANGED
function formateNumber ($n) {
$areaCode = substr($n, 0, 3);
$part1 = substr($n, 3, 3);
$part2 = substr($n, 6, 4);
return "($areaCode) $part1-$part2";
}
function shorten ($str, $mLen, $elp) {
if (strlen($str) <= $mLen) {
return $str;
} else {
return rtrim(substr($str, 0, $mLen)) . $elp;
}
}
do {
$number = $data["number"];
$sidebarQ = "
SELECT *
FROM (
SELECT *
FROM messages
WHERE deleted NOT LIKE '%$number%'
AND (
`from`='$number'
OR
`to`='$number'
)
ORDER BY `timestamp` DESC
) as mess
GROUP BY `id`
ORDER BY `timestamp` DESC";
$query = $mysqli->query($sidebarQ);
if ($query->num_rows == 0) {
echo 'data: null' . $number;
echo "\n\n";
} else {
$qr = array();
while($row = $query->fetch_assoc()) {
$qr[] = $row;
}
foreach ($qr as $c) {
$id = $c["id"];
if (!isset($store->{$id})) {
$store->{$id} = $c["messageId"];
$go = true;
} else {
if ($store->{$id} != $c["messageId"]) {
$go = true;
$store->{$id} = $c["messageId"];
}
}
}
if($go == true) {
$el = $n = "";
foreach ($qr as $rows) {
$to = $rows["to"];
$id = $rows["id"];
$choose = $to == $number ? $rows["from"] : $to;
$nameQuery = $mysqli->query("SELECT `savedname` FROM `contacts` WHERE `friend`='$choose' AND `number`='$number'");
$nameGet = $nameQuery->fetch_assoc();
$hasName = $nameQuery->num_rows == 0 ? formateNumber($choose) : $nameGet["savedname"];
$new = $mysqli->query("SELECT `id` FROM `messages` WHERE `to`='$number' AND `tostatus`='0' AND `id`='$id'")->num_rows;
if ($new > 0) {
$n = "<span class='new'>" . $new . "</span>";
}
$side = "<span style='color:#222'>" . ($to == $number ? "To you:" : "From you:") . "</span>";
$el .= "<div class='messageBox sBox" . ($nameQuery->num_rows == 0 ? " noname" : "") . "' onclick=\"GLOBAL.load($id, $choose)\" data-id='$id'><name>$hasName</name><div>$side " . shorten($rows["message"], 25, "...") . "</div>$n</div>";
}
echo 'data: '. $el;
echo "\n\n";
$go = false;
}
}
echo " ";
ob_flush();
flush();
sleep(2);
} while(true);
?>
I would also like to note, that this infinite loop shouldn't be causing this to happen. This is just how SSE's are set up usually and it is even done so on the MDN website.
No doubt by now you have figured this out but on the offchance you have not I used code like the following on a couple of sse scripts and it worked like a charm. The code below is generic and does not feature your sql or recordset processing but the idea is sound(!?)
<?php
set_time_limit( 0 );
ini_set('auto_detect_line_endings', 1);
ini_set('mysql.connect_timeout','7200');
ini_set('max_execution_time', '0');
date_default_timezone_set( 'Europe/London' );
ob_end_clean();
gc_enable();
header('Content-Type: text/event-stream');
header('Cache-Control: no-cache');
header('Access-Control-Allow-Credentials: true');
header('Access-Control-Allow-Methods: GET');
header('Access-Control-Expose-Headers: X-Events');
if( !function_exists('sse_message') ){
function sse_message( $evtname='chat', $data=null, $retry=1000 ){
if( !is_null( $data ) ){
echo "event:".$evtname."\r\n";
echo "retry:".$retry."\r\n";
echo "data:" . json_encode( $data, JSON_FORCE_OBJECT|JSON_HEX_QUOT|JSON_HEX_TAG|JSON_HEX_AMP|JSON_HEX_APOS );
echo "\r\n\r\n";
}
}
}
$sleep=1;
$c=1;
$pdo=new dbpdo();/* wrapper class for PDO that simplifies using PDO */
while( true ){
if( connection_status() != CONNECTION_NORMAL or connection_aborted() ) {
break;
}
/* Infinite loop is running - perform actions you need */
/* Query database */
/*
$sql='select * from `table`';
$res=$pdo->query($sql);
*/
/* Process recordset from db */
/*
$payload=array();
foreach( $res as $rs ){
$payload[]=array('message'=>$rs->message);
}
*/
/* prepare sse message */
sse_message( 'chat', array('field'=>'blah blah blah','id'=>'XYZ','payload'=>$payload ) );
/* Send output */
if( #ob_get_level() > 0 ) for( $i=0; $i < #ob_get_level(); $i++ ) #ob_flush();
#flush();
/* wait */
sleep( $sleep );
$c++;
if( $c % 1000 == 0 ){/* I used this whilst streaming twitter data to try to reduce memory leaks */
gc_collect_cycles();
$c=1;
}
}
if( #ob_get_level() > 0 ) {
for( $i=0; $i < #ob_get_level(); $i++ ) #ob_flush();
#ob_end_clean();
}
?>
While this is not a direct answer as to the problem, try using this method to find the error.. Your not getting errors, but this should help you find them maybe?
Basically you want to have a simple PHP script which includes your main script, but this page enables errors... Example below..
index.php / Simple Error Includer
<?php
ini_set('display_errors',1);
ini_set('display_startup_errors',1);
error_reporting(-1);
require "other.php";
?>
other.php / You Main Script
<?php
ini_set('display_errors',1);
ini_set('display_startup_errors',1);
error_reporting(-1);
weqwe qweqeq
qweqweqweqwe
?>
If you create a setup like this, if you view index.php you will see the following error Parse error: syntax error, unexpected 'qweqeq' (T_STRING) in /var/www/html/syntax_errors/other.php on line 5 because it does not have an invalid syntax on the main page and allows any includes to be error checked..
But if you where to view other.php, you would simply get a white / blank page because its unable to validate the whole page/script.
I use this method in my projects, that way regardless of what i do in other.php or any linked php pages, i will see an error report for them.
Please understand the code before commenting
to say this disables error control means you did not bother to RTM
Fill the buffer
Another issue in the past that i remember was filling the buffer before it would output to the browser. So try something like this before your loop.
echo str_repeat("\n",4096); // Exceed the required browser threshold
for($i=0;$i<70;$i++) {
echo "something as normal";
flush();
sleep(1);
}
Examples at http://www.sitepoint.com/php-streaming-output-buffering-explained/
It seems like the sleep function is interfering with the output. Putting the sleep function AFTERWARDS did work:
<?php
while(true) {
echo "data: This is the message.";
ob_flush();
flush();
sleep(3);
}
As other people suggest, I would encourage to use AJAX instead of an infinite loop, but that was not your question.
One thing I have noticed here is sleep() function in combination with ob_start() and - THERE IS NO - ob_start() anywhere in the full code example, yet there is flush() and ob_flush() ..
What are you flushing anyway?
And why not simply ob_end_flush() ?
The thing is that sleep() than echo(), than sleep() again, than echo() again, etc, etc.. has no effect when output buffering is turned on. Sleep function works as expected when output buffering is not in play - in between. In fact, it might *(and it will) produce quite unexpected results, and those results won't be the one we want to see.
The following code works fine here, also using Mayhem his str_repeat function to add 4k of data (that is usually the minimum for a tcp packet to be flushed by php)
echo str_repeat(' ', 4096);
while(true)
{
echo "data: This is the message.";
flush();
sleep(3);
}
Instead of using loop try this code given below which is working(tested myself) fine as per your requirement
echo "data: This is the message.";
$url1="<your-page-name>.php";
header("Refresh: 5; URL=$url1");
what this will do is it will call itself every 5 seconds (in your case set it to 3 instead of 5) and echo the output.
I am going to take a chance and state the obvious,
you could query the server every 3 seconds, and let the client do the waiting...
This could be done easily with javascript
for example, try this code and name if file.php
<?php
$action='';
if (array_key_exists('action',$_GET))
{$action=$_GET['action'];}
if ($action=='poll')
{
echo "this message will be sent every 3 sec";
}
else
{
?><HTML><HEAD>
<SCRIPT SRC="http://code.jquery.com/jquery-2.1.3.min.js"></SCRIPT>
<SCRIPT>
function doPoll()
{
$('#response').append($.get("file.php?action=poll"));
setTimeout(doPoll, 3000);
}
doPoll();
</SCRIPT>
</HEAD><BODY><DIV id="response"></DIV></BODY></HTML><?php
}
Could it be as simple as the script timing out?
Eventually PHP scripts self terminate if they run for too long. The solution for when you don't want this to happen is to keep resetting the time out.
So a simple addition might be all you need:
<?php
while(true) {
echo "data: This is the message.";
set_time_limit(30);
sleep(3);
ob_flush();
flush();
}
?>
Of course, that might not be it but my gut instinct is that this is the problem.
http://php.net/manual/en/function.set-time-limit.php
UPDATE: I noticed in the comments that you are using some free hosting. If they are running PHP in safe mode then you cannot reset your timeout.
I had the same issue and finally found the easy and quick solution on kevin choppin's blog:
Session Locks
First and foremost, if you're using sessions for whatever reason you will need to make them read-only on the stream. If they're writable, this will lock them everywhere else, so any page loads will hang while the server waits for them to become writable again. This is easily fixed by calling; session_write_close();
I suggest using if() statement instead of using while. And in your case your condition is always true, hence it is in infinite loop.
So I need a little help, is there a better way to have php wait before executing the next line of code?
I tried:
$response = $_POST[response];
echo "</br>".$response;
if (strpos($response,'no') !== false) {
sleep(2);
echo "</br>";
echo 'Why not?';
}
But this method does not display the
echo "</br>".$response;
before it sleeps.
It sleeps for the 2 seconds, then displays the response.
How can I get it to echo $response, then wait 2 seconds before is says "Why Not"
Thank you in advance.
Flush your buffer (UPDATE):
<?
$response = $_POST[response];
echo "</br>".$response;
ob_end_flush();
flush();
if (strpos($response,'no') !== false) {
sleep(2);
echo "</br>";
echo 'Why not?';
}
?>
References: http://php.net/manual/en/function.ob-flush.php, http://php.net/flush
You have to use flush the buffer content to see the results
#apache_setenv('no-gzip', 1);
#ini_set('zlib.output_compression', 0);
ob_start();
$response = $_POST[response];
echo "<br />".$response;
ob_flush();
flush();
if (strpos($response,'no') !== false) {
sleep(2);
echo "<br />";
echo 'Why not?';
}
I am using both ob_flush() and flush() as stated in http://php.net/manual/en/function.flush.php but just see what works. Sometimes only using flush() also works, depending on the server config.
Be aware of gzip/deflate. You can't deflate an output stream and in the middle of it output the buffer. You can either turn it off by using the htaccess or with the 2 first lines of the code
It looks like the output buffer isn't being flushed before the sleep call. You can indeed control this manually as Pentium10 Points out: https://stackoverflow.com/a/3078873/1461223
I have a script that pulls users from the DB, prepares an XMPP message, loops through each user and sends the XMPP message, then logs that the message was sent. Easily running through 1000 users plus. This is a server side API script that is called from a mobile device. The mobile device is waiting to receive a success JSON response. The user experience should be quick, I don't want the mobile user waiting for more than a few seconds for the response.
Problem is its taking a fair amount of time for the script to loop through all users, so my initial solution was to use ob_flush() - note these are merely test scripts to see if the planned method works:
ob_start();
$profiles_ar = array(
"reach" => 30,
);
$return_ar = array(
"success" => $profiles_ar['reach'],
);
echo json_encode($return_ar);
$buffer = str_repeat(" ", 4096); // Note apparently the buffer must be "filled" with 4096 characters (bytes?) for ob_flush() to work before sleep() occurs.
echo $buffer;
ob_flush();
flush();
for($i=0;$i < $profiles_ar['reach']; $i++)
{
sleep(1);
}
echo "finshed: ".$i;
ob_flush();
flush();
That's not working, nothing gets output until the script has finished - have I missed something with OB technique?
...... so did some searching and came up with this:
register_shutdown_function('process_after');
$profiles_ar = array(
"reach" => 10,
);
$return_ar = array(
"success" => $profiles_ar['reach'],
);
echo json_encode($return_ar);
echo $buffer;
exit;
function process_after()
{
global $profiles_ar;
for($i=0;$i < $profiles_ar['reach']; $i++)
{
sleep(1);
}
echo "finshed: ".$i;
}
this one works on mac, but not on the server....
Anyone got any ideas? If i cant get this technique of outputting the response JSON before the main processing to work, then my only hope is to build a queue in the DB and run a cron job........ ;(
Is output_buffering enabled in php.ini?
http://php.net/manual/en/outcontrol.configuration.php
I would refactor the creation of the xmpp message in it's own file and then use ajax calls to send each one. That way you aren't waiting on each message to succeed.
Solution is to add :
echo " ";
ob_flush(); flush;
inside the loop....
ob_start();
$profiles_ar = array(
"reach" => 10,
);
$return_ar = array(
"success" => $profiles_ar['reach'],
);
echo json_encode($return_ar);
for($i = 0; $i < 5000; $i++)
{
echo " ";
ob_flush(); flush;
}
echo $buffer;
ob_flush();
flush();
ob_end_flush();
for($i=0;$i < $profiles_ar['reach']; $i++)
{
sleep(1);
}
echo "finshed: ".$i;
ob_flush();
flush();
ob_end_flush();
This repeatedly forces the output from the first iteration of the loop and eventually kicks in.
I'm using Laravel and I need to output data as it happens. When I attempt to load the page outside Laravel, it works just fine. If I use this inside Laravel, it doesn't flush, it waits until the end and prints the results.
view.php
<?php
if (ob_get_level() == 0) ob_start();
for ($i = 0; $i <= 10; $i++){
echo "<br> Line to show. $i";
echo str_pad('',4096)."\n";
ob_flush();
flush();
sleep(1);
}
ob_end_flush();
?>
Figured it out, I needed to add ob_flush();
Update, for anyone coming here.
The above solutions didn't work for me. What worked, is adding the
header('X-Accel-Buffering: no');
before any output.
Found it here: https://laracasts.com/discuss/channels/laravel/live-output-in-blade-template-ob-flush
This sequence worked for me.
ob_implicit_flush(true);
echo "Processing ... "; // Or give out JSON output
ob_flush();
sleep(5); //A time-consuming synchronous process (SMTP mail, maybe?)
echo "Done";