How to periodically change a value in HTML with PHP

Question

Let's say that I want a webpage that displays PHP memory usage in realtime.

I can get memory usage with:

memory_get_peak_usage(1)

I can print it in an input field like this:

<form>
    Memory usage: <input type="text" name="FirstName" value="<?echo memory_get_peak_usage(1);?>">
</form>

and an option to update the value in the input field would be reloading the page, but how can I do it without refreshing?

I bet I have to use GET/POST methods.

while (1)
{
    $mem =  memory_get_peak_usage(1);
    sleep(0.5);
    update_inputField_value($mem);
}

once page loads, the peak memory usage wont change so refreshing it is pointless. — , Feb 16 '14 at 22:57
I don't get your point. My initial purpose was to monitor memory usage to debug my Wordpress site, and understand which function I wrote was using too much memory. I could have a browser window from which I load Wordpress and another one that keep refreshing and tells me when too much memory is used. — Alain1405, Feb 16 '14 at 23:03
once the page is output, php is finished, so memory for that process is finished. — , Feb 16 '14 at 23:05
The function only returns the memory usage of the current request so you won't be able to achieve what you would like to. You need a `profiler` such as `XHProf` or `Xdebug`. — Andrew Mackrodt, Feb 16 '14 at 23:08
Ok, thanks to have brought me to the point where I give up. :) — Alain1405, Feb 16 '14 at 23:16
you need to call memory_get_peak_usage(1) only once, after php has created the HTML. — , Feb 16 '14 at 23:18

score 3 · Accepted Answer · edited May 23 '17 at 12:03

you have to use something like Long polling, where you have a website that keeps the client waiting for a request and occasionally delivers some html as needed; or an implementation like socket.io for nodejs that allows you to perform actions like you're looking for natively.

Here's a SO question on longpolling with PHP: How do I implement basic "Long Polling"?

here's a question on how to use a socket.io like implementation with php: Using PHP with Socket.io

A final alternative is to have an ajax call on a timer that hits a webservice that pulls the value every few seconds giving a real-time like feel to the page even though it's a periodic refresh.

Say you're using jquery:

setTimeout(function(){
    $.ajax({
        dataType: "json",
        url: 'memoryUsage.php',
        success: function(data){
            $("#FirstName").val(data.memory)
        }
    });
}, 5000); //5 seconds

assuming your memoryUsage.php echos a value that looks like {memory:"some value"}

keep in mind all of these options are pretty memory and network traffic intensive.

How to periodically change a value in HTML with PHP

1 Answers1