Is it possible to set a delay between 2 portion of code in PHP? I want something like this-
<?php
function firstFunc(){
echo "anything";
}
function secondFunc(){
echo "something";
}
// call first fumction
firstFunc();
// I want the script to wait for 2 seconds here, then call second function
secondFunc();
Is it possible?
If you want to delay the execution of something, you can use the sleep($seconds) function. Here's what the documentation says
Delays the program execution for the given number of seconds.
It returns zero on success and false on error.
So you can do something like:
<?php
function firstFunc(){
echo "anything";
}
function secondFunc(){
echo "something";
}
// call first function
firstFunc();
sleep(2); //Delays execution for 2 seconds.
secondFunc();
?>
Keep in mind though, PHP is a server side language. The only thing the client will receive from a PHP script(if the client has to receive anything at all) is HTML(or CSS, JS and so on). So when you run this code, the page will show nothing for 2 seconds and then output anything and something together because the delay is happening at a server level, and not on client machine. If you want a kind a delay where something is visible on the screen and then after 2 seconds anything appears, you want to use JavaScript.
Hope this helps :)
You should use function sleep(int seconds)
Related
I have a block of code and want to run it after certain time intervals, say after every 3 seconds. If I get required result it should die otherwise another request will be sent after 3 seconds. Any idea to do it with php.
Thanks in advance for any help
You can sleep in a loop:
while (true) {
$result = doSomething;
if (resultIsGood) {
break;
}
sleep(3);
}
If you don't want to keep the browser waiting, you can look up ignore_user_abort() solutions on Google.
If what you want to execute MySQL queries (and nothing else), maybe using the MySQL event scheduler could fit your need:
http://dev.mysql.md/doc/refman/5.5/en/events-overview.html
Is it possible to set a "callback function" that do something instead of returning an error whe the time limit is reached?
You could remove the time limit (set_time_limit(0)), and then keep track of the time the PHP script started executing and make a comparison with the current time.
<?php
$startTime = microtime();
// Whatever you need to do...
// Place this where it needs to be in the context of your application.
if (microtime() - $startTime > 15000) {
// Time's up!
}
I don't think so...that kind of defeats the point of the function to begin with... I think if you wanna do something like that, set it to 0 (no time limit) and keep track of the time a different way and do something after X time.
As others have said no.
If your script is timing out because of external factors (like it doesn't come back from a single function call), then your only remedy may be to use pcntl_alarm and pcntl_signal. Allthough I'm not sure these can be used in sapi's other then CLI.
You can Try this one :
http://www.php.net/register_shutdown_function
function shutdown()
{
// This is our shutdown function, in
// here we can do any last operations
// before the script is complete.
echo 'Script executed with success', PHP_EOL;
}
register_shutdown_function('shutdown');
i have a script which output the percentage of completeness : 10% 20%...100% done.
Can i bring that output to the web?
I call it using jquery ajax:
$.post('dojob.php?id=jobid');
thanks Arman
If I'm understanding what you want, you're looking to call dojob.php and have it return it's progress at certain intervals. This can't be done with one ajax call.
If you need to do this, you will have to call dojob.php but then every x seconds make a separate call to somehow monitor it's progress. For instance, lets say you have checkStatus.php which can give you the progress of dojob. So you call dojob.php, then every 5 seconds call checkStatus.php which will return your % complete of dojob.
Simiarly, you could call dojob and have it kick off a separate thread and then return. THen every x seconds call checkStatus.php, which will either return the % complete, or upon completion return the result of dojob.
to simply write it, try the following code
html:
<div id="progress"></div>
js code:
$('#progress').load('dojob.php?id=jobid');
The question sort of says it all - is there a function which does the same as the JavaScript function setTimeout() for PHP? I've searched php.net, and I can't seem to find any...
There is no way to delay execution of part of the code of in the current script. It wouldn't make much sense, either, as the processing of a PHP script takes place entirely on server side and you would just delay the overall execution of the script. There is sleep() but that will simply halt the process for a certain time.
You can, of course, schedule a PHP script to run at a specific time using cron jobs and the like.
There's the sleep function, which pauses the script for a determined amount of time.
See also usleep, time_nanosleep and time_sleep_until.
PHP isn't event driven, so a setTimeout doesn't make much sense. You can certainly mimic it and in fact, someone has written a Timer class you could use. But I would be careful before you start programming in this way on the server side in PHP.
A few things I'd like to note about timers in PHP:
1) Timers in PHP make sense when used in long-running scripts (daemons and, maybe, in CLI scripts). So if you're not developing that kind of application, then you don't need timers.
2) Timers can be blocking and non-blocking. If you're using sleep(), then it's a blocking timer, because your script just freezes for a specified amount of time.
For many tasks blocking timers are fine. For example, sending statistics every 10 seconds. It's ok to block the script:
while (true) {
sendStat();
sleep(10);
}
3) Non-blocking timers make sense only in event driven apps, like websocket-server. In such applications an event can occur at any time (e.g incoming connection), so you must not block your app with sleep() (obviously).
For this purposes there are event-loop libraries, like reactphp/event-loop, which allows you to handle multiple streams in a non-blocking fashion and also has timer/ interval feature.
4) Non-blocking timeouts in PHP are possible.
It can be implemented by means of stream_select() function with timeout parameter (see how it's implemented in reactphp/event-loop StreamSelectLoop::run()).
5) There are PHP extensions like libevent, libev, event which allow timers implementation (if you want to go hardcore)
Not really, but you could try the tick count function.
http://php.net/manual/en/class.evtimer.php is probably what you are looking for, you can have a function called during set intervals, similar to setInterval in javascript. it is a pecl extension, if you have whm/cpanel you can easily install it through the pecl software/extension installer page.
i hadn't noticed this question is from 2010 and the evtimer class started to be coded in 2012-2013. so as an update to an old question, there is now a class that can do this similar to javascripts settimeout/setinterval.
Warning: You should note that while the sleep command can make a PHP process hang, or "sleep" for a given amount of time, you'd generally implement visual delays within the user interface.
Since PHP is a server side language, merely writing its execution output (generally in the form of HTML) to a web server response: using sleep in this fashion will generally just stall or delay the response.
With that being said, sleep does have practical purposes. Delaying execution can be used to implement back off schemes, such as when retrying a request after a failed connection. Generally speaking, if you need to use a setTimeout in PHP, you're probably doing something wrong.
Solution: If you still want to implement setTimeout in PHP, to answer your question explicitly: Consider that setTimeout possesses two parameters, one which represents the function to run, and the other which represents the amount of time (in milliseconds). The following code would actually meet the requirements in your question:
<?php
// Build the setTimeout function.
// This is the important part.
function setTimeout($fn, $timeout){
// sleep for $timeout milliseconds.
sleep(($timeout/1000));
$fn();
}
// Some example function we want to run.
$someFunctionToExecute = function() {
echo 'The function executed!';
}
// This will run the function after a 3 second sleep.
// We're using the functional property of first-class functions
// to pass the function that we wish to execute.
setTimeout($someFunctionToExecute, 3000);
?>
The output of the above code will be three seconds of delay, followed by the following output:
The function executed!
if you need to make an action after you execute some php code you can do it with an echo
echo "Success.... <script>setTimeout(function(){alert('Hello')}, 3000);</script>";
so after a time in the client(browser) you can do something else, like a redirect to another php script for example or echo an alert
There is a Generator class available in PHP version > 5.5 which provides a function called yield that helps you pause and continue to next function.
generator-example.php
<?php
function myGeneratorFunction()
{
echo "One","\n";
yield;
echo "Two","\n";
yield;
echo "Three","\n";
yield;
}
// get our Generator object (remember, all generator function return
// a generator object, and a generator function is any function that
// uses the yield keyword)
$iterator = myGeneratorFunction();
OUTPUT
One
If you want to execute the code after the first yield you add these line
// get the current value of the iterator
$value = $iterator->current();
// get the next value of the iterator
$value = $iterator->next();
// and the value after that the next value of the iterator
// $value = $iterator->next();
Now you will get output
One
Two
If you minutely see the setTimeout() creates an event loop.
In PHP there are many libraries out there E.g amphp is a popular one that provides event loop to execute code asynchronously.
Javascript snippet
setTimeout(function () {
console.log('After timeout');
}, 1000);
console.log('Before timeout');
Converting above Javascript snippet to PHP using Amphp
Loop::run(function () {
Loop::delay(1000, function () {
echo date('H:i:s') . ' After timeout' . PHP_EOL;
});
echo date('H:i:s') . ' Before timeout' . PHP_EOL;
});
Check this Out!
<?php
set_time_limit(20);
while ($i<=10)
{
echo "i=$i ";
sleep(100);
$i++;
}
?>
Output:
i=0 i=1 i=2 i=3 i=4 i=5 i=6 i=7 i=8 i=9 i=10
I am new to this site, so I really hope I will provide all the necessary information regarding my question.
I've been trying to create a "new message arrived notification" using long polling. Currently I am initiating the polling request by window.onLoad event of each page in my site.
On the server side I have an infinite loop:
while(1){
if(NewMessageArrived($current_user))break;
sleep(10);
}
echo $newMessageCount;
On the client side I have the following (simplified) ajax functions:
poll_new_messages(){
xmlhttp=GetXmlHttpObject();
//...
xmlhttp.onreadystatechange=got_new_message_count;
//...
xmlhttp.send();
}
got_new_message_count(){
if (xmlhttp.readyState==4){
updateMessageCount(xmlhttp.responseText);
//...
poll_new_messages();
}
}
The problem is that with each page load, the above loop starts again. The result is multiple infinite loops for each user that eventually make my server hang.
*The NewMessageArived() function queries MySQL DB for new unread messages.
*At the beginning of the php script I run start_session() in order to obtain the $current_user value.
I am currently the only user of this site so it is easy for me to debug this behavior by writing time() to a file inside this loop. What I see is that the file is being written more often than once in 10 seconds, but it starts only when I go from page to page.
Please let me know if any additional information might help.
Thank you.
I think I found a solution to my problem. I would appreciate if anyone could tell, if this is the technique that is being used in COMET and how scalable this solution.
I used a user based semaphore like this:
$sem_id = sem_get($current_user);
sem_acquire($sem_id);
while(1){
if(NewMessageArrived($current_user))break;
sleep(10);
}
sem_release($sem_id);
echo $newMessageCount;
It seems common for long-polling requests to timeout after 30 seconds. So in your while loop you could echo 'CLOSE' after 30 seconds.
while(!$new_message && $timer < 30){
$new_message = NewMessageArrived($current_user);
if(!$new_message) {
sleep(10);
$timer += 10;
}
}
if($newMessageCount) {
echo $newMessageCount;
} else {
echo 'CLOSE';
}
In the Javascript, you can listen for the CLOSE.
function poll_new_messages(){
xmlhttp=GetXmlHttpObject();
//...
xmlhttp.onreadystatechange=got_new_message_count;
//...
xmlhttp.send();
}
function got_new_message_count(){
if (xmlhttp.readyState==4){
if(xmlhttp.responseText != 'CLOSE') {
updateMessageCount(xmlhttp.responseText);
}
//...
poll_new_messages();
}
}
Now, the PHP will return a response within 30 seconds, no matter what. If you use stays on the page, and you receive a CLOSE, you just don't update the count on the page, and re-ask.
If the user moves to a new page, your PHP instance will stop the loop regardless within 30 seconds, and return a response. Being on a new page though, the XHR that cared about that connection no longer exists, so it won't start up another loop.
You might try checking connection_aborted() periodically. Note that connection_aborted() might not pick up on the fact that the connection has in fact been aborted until you've written some output and done a flush().
In fact, just producing some output periodically may be sufficient for php to notice the connection close itself, and automatically kill your script.