I have a php file that is fired by a cronjob every minute.
When the php file is fired it updates the database, sleeps, etc
It is programmed like this:
$start = microtime(true);
set_time_limit(10);
for($i=0;$i<5;$i++)
{
updateDB();
time_sleep_until($start + $i + 1);
}
If this piece of code is run i don't see any changes happening in the database. Another thing i notices is when i echo something out i is printed when the loop is ended in one piece.
[edit] I tried using flush and ob_flush, but it still didn't print line for line[/edit]
What can i do to avoid these errors. The database needs to be updated.
Another thing i was wondering is what the best way is to log this kind of thing. Can i log the results to a log file.
The loop itself looks fine. If it isn't updating your database, the error must be in your updateDB() function.
As to the echo thing. The output of scripts is often buffered. To force PHP to print it right away, you can call either call flush() whenever you want the output flushed, or you can just call ob_implicit_flush() at the top of the script and it will flush automatically every time you print something.
Also, if you are calling the script via a browser, the browser itself may further buffer the response before showing it to you.
And as to the logging, the simplest way is to pick a file somewhere and just use file_put_contents() to print whatever you want logged. Note the FILE_APPEND flag for the third parameter.
Looks like you are running from command line, in this case you may want to write to stderr so that there is no buffering. $stderr = fopen('php://stderr', 'w');
In the case of logging, just open a file, write to it, and close it. (fopen, fwrite, fclose);
Related
When single-stepping through PHP code during debugging (e.g. in Netbeans) I want to see PHP output in my browser immediately. This can be achieved (at least when using PHP7.2 and Firefox) by including the following at the start of the PHP code:
ob_implicit_flush ();
while (#ob_end_flush());
This ensures that things like
echo "foo\n";
immediately result in 'foo' being displayed in the web browser rather than when the output buffer is due for a flush or the PHP code exits upon completion or error.
But is there a way to achieve this by editing php.ini so I don't have to include it in every bit of PHP code to be debugged? (I understand this will result in a performance penalty, but this is for development and debugging purposes only.)
Flushing the output buffer is an implicit action that the developer must make, so isn't something that can be toggled on or off in the php.ini.
However, PHP does have a feature called ticks, which allows the developer to register a callback function to be called every X lines of code that are executed.
See register_tick_function, where you can define your own callback function to perform the flush, and have it run in between every statement in your program. This will obviously kill performance, and there is probably a better way of achieving what you're trying to do.
Example:
declare(ticks=1);
function autoFlushBuffer() {
ob_implicit_flush ();
while (#ob_end_flush());
}
register_tick_function("autoFlushBuffer", true);
// The following lines will appear in your web browser one by one:
echo "one";
sleep(1);
echo "two";
sleep(1);
echo "three";
sleep(1);
I'm trying to find a way in which I can echo out the output of an exec call, and then flush that to the screen while the process is running. I have written a simple PHP script which accepts a file upload and then converts the file if it is not the appropriate file type using FFMPEG. I am doing this on a windows machine. Currently my command looks like so:
$cmd = "ffmpeg.exe -i ..\..\uploads\\".$filename." ..\..\uploads\\".$filename.".m4v 2>&1";
exec( $cmd, $output);
I need something like this:
while( $output ) {
print_r( $output);
ob_flush(); flush();
}
I've read about using ob_flush() and flush() to clear the output buffer, but I only get output once the process has completed. The command works perfectly, It just doesn't update the Page while converting. I'd like to have some output so the person knows what's going on.
I've set the time out
set_time_limit( 10 * 60 ); //5 minute time out
and would be very greatful if someone could put me in the right direction. I've looked at a number of solutions which come close one Stackoverflow, but none seem to have worked.
Since the exec call is a blocking call you have no way of using buffers to get status.
Instead you could redirect the output in the system call to a log file. Let the client query the server for progress update in which case the server could parse the last lines of the log file to get information about current progress and send it back to the client.
exec() is blocking call, and will NOT return control to PHP until the external program has terminated. That means you cannot do anything to dump the output on a line-by-line basis because PHP is suspended while the external app is running.
For what you want, you need to use proc_open, which returns a filehandle you can read from in a loop. e.g.
$fh = proc_open('.....');
while($line = fgets($fh)) {
print($line);
flush();
}
There are two problems with this approach:
The first is that, as #Marc B notes, the fact that exec will block until it's finished. You'll have to devise some way of measuring progress.
The second is that using ob_flush() in this way amounts to holding the connection between server & client open and dribbling the data out a little at a time. This is not something that the HTTP protocol was designed for and while it might work sometimes, it's not going to work consistently - different browsers and different servers will time out differently. The better way to do it is via AJAX calls: using Javascript's setTimeout() function (or setInterval()), make a call to the server periodically and have the server send back a progress report.
Good day!
I am having some issues with getting the echo statement to output before the execution of the exec()
<?
if (isset($_POST['ipaddress'])) {
$escaped_command = escapeshellcmd($_POST['ipaddress']);
if(filter_var($escaped_command, FILTER_VALIDATE_IP)) {
echo "Gleaning ARP information, please wait..";
$command = exec('sudo /sbin/getarp.exp');
The echo statement is being outputted after the execution of the $command. The execution time can be anywhere from 15-30 seconds depending on how large the ARP table on the remote router is. Is there an order of operations that I am not aware of? It appears that all the statements within the if statement are executed in parallel and not by line by line as I had assumed.
I would rather not a solution be provided, but some documentational links that would lead me to finding a solution. I have searched what I could, but was not able to find a viable solution.
Any help would be appreciated.
Thanks.
This is happening because the script will run in its entirety before any result/output is sent to the browser.
In PHP there is a concept of "output buffering".
Whenever you output something (e.g. using echo, print, etc.) the text is thrown into a buffer. This buffer is only sent at certain times (at the end of the request, for instance, or when the buffer is full).
In order to empty the buffer (to "flush" it) you need to do it manually. The flush() function will do this. Sometimes you also need to call ob_flush() (this is if you have opened custom output buffers yourself). It is generally a good idea to just call both functions and be done with it:
echo 'Wait a few seconds...';
flush(); ob_flush();
sleep(3);
echo ' aaand we are done!';
See Output Buffering Control for more information on output buffering in PHP.
This is probably an issue with the output buffer. PHP buffers output and writes it to the browser in chunks. Try adding a call to ob_flush() between the echo and the exec(); this will force PHP to write the current contents of the buffer to the browser.
By default, php does not send any of the output until the php script is done running completely. There is a solution. However, I hear it is a little browser dependent. I would test it on different systems and browsers to see if it is working:
ob_implicit_flush (true)
Put that before any of your echo/print commands and that should allow anything printed to show right up on the browser.
A more universal approach would be to integrate your page with asynchronous javascript. A process commonly referred to as "AJAX". It is a little more difficult because it requires the use of many interacting scripts, some client-side and some server-side. However, AJAX is the defacto way to do thing like this on the web.
I have a php script that uses cURL and takes about 10-15 minutes to execute. What it does, it parses about 1000 pages looking for specific matches and throughout the script I have diagnostic messages echo'ed out, like "Going to the next page", "Found a match", "Error loading page" ... The way it works now (and the way that it's normal) is it executes for like 10 minutes and only then spits out all my custom messages.
I would like to be able to display those messages as they happen, not when the script is done executing. I was thinking something like AJAX would do it, but am not sure how it would work. Any tips are greatly appreciated. Thanks.
So, this is a old post but I found a solution for this. As I also have to make the same thing, output when the script is still running. Not any answer from here helped.
First of all, I am using Win32 server(production) and XAMPP as local for tests. This example is just a proof of concept and can be modified as you please.
<?php
ob_implicit_flush(true);
for($i=1; $i<=10; $i++){
echo "$i ...<br>";
for($k = 0; $k < 40000; $k++) echo ' ';
sleep(1);
}
?>
So, we open output buffer as implicit. Then we make a demo loop to count from 1 to 10 and display the values as they are been processed. Second loop will fill in the browsers buffer. And finally to check if everything is working well we make a sleep for 1 second. Otherwise the script will run too fast and we could not know if we achieved the goal.
Hope this helps !
You could create a staging table.
The PHP script could, instead of echo'ing the message, store them into a database table (possibly memory table for performance).
You could then periodically poll a seperate PHP script using ajax, which would query the table, and return any new messages to the client.
Use flush to immediately send output to the browser, by flushing the output buffer.
echo "foo";
flush();
echo "bar";
flush();
Actually you're looking for something like flush and ob_flush, however bear in mind that there are a lot of factors that can prevent your output from being flush'd as it happens.
From the flush documentation you'll get:
Several servers, especially on Win32, will still buffer the output from your script until it terminates before transmitting the results to the browser.
Server modules for Apache like mod_gzip may do buffering of their own that will cause flush() to not result in data being sent immediately to the client.
I'm using the #ob_flush() after every echo. In this example PHP_EOL creates a new line after $string
function output($string){
echo $string.PHP_EOL;
#ob_flush();
}
Basically, have your script write HTML output to a temporary log file. Then use ajax to periodically update the end-user's browser with the temporary log file. jQuery will make quick work of this.
Ajax is the only guaranteed way to get it to work on all browsers. Here is a quote from PHP's flush page.
flush() may not be able to override
the buffering scheme of your web
server and it has no effect on any
client-side buffering in the browser.
It also doesn't affect PHP's userspace
output buffering mechanism. This means
you will have to call both ob_flush()
and flush() to flush the ob output
buffers if you are using those.
Sounds to be like you have output buffering turned on.
Calling ob_end_flush() will print what's currently in the buffer, and turn off the buffer for the rest of the script execution.
You can use the flush() function to send all the content of the buffer to the client. http://php.net/manual/fr/function.flush.php
You could use both flush and ob_flush, reminding to set the content type header:
<?php
header( 'Content-type: text/html; charset=utf-8' );
for( $i = 0 ; $i < 10 ; $i++ ){
echo $i . '<br>';
flush();
ob_flush();
sleep(1);
}
Source: dermeister note in php.net ob_flush page.
Tested on Firefox 42.0 and Chrome 46.0
How does the server knows that i've closed the browser in a code like this?
<?php
$i = 0;
while (1) {
echo "a";
flush();
$fp = fopen("$i.txt", "w");
fclose($fp);
sleep(1);
$i++;
}
?>
If i close the browser, the script stops and no more files are created.
This is because when you try to output something, such as echo "a"; flush();", PHP sees that the request has been aborted, and therefore stops the request.
Just a quick note. This only happens when you output something. I'm guessing this is because PHP was primarily used for templating, and designed mainly for outputting content. Well, if the content is not going to go anywhere, why continue processing the script?
If you don't want it to stop. Do one of the following:
Option A: Don't output anything.
flush() and echo are both considered outputs, along with many other functions. PHP only checks to see if a user has aborted when it goes to send content, so not outputting anything will make sure it doesn't check. Although that is probably not as reliable as...
Option B: use ignore_user_abort(true)
This will make sure that the script continues to output even if the user leaves the page. You can then check with connection_aborted() to find out if the connection has been aborted.
You can read all of this on PHP's Connection Handling Documentation.