Show real-time loop result

Question

I’m using a loop to send emails from an array. Every time the loop runs the function sleep(4); is executed.

The problem is that php output only happens at the end, ie the lines echo "</br>n:".$ne."&nbsp".$user["email"]."</br> >>enviado</br>"; are shown in output all at once and after all loops run.

I would like as each loop runs, the echo function is displayed (one by one and not at once at the end).

foreach($users as $user) {
  $message->setTo($user["email"], $user["nome"]);
echo "\n";sleep(4);
  flush(); 
  ob_end_flush();  
  echo date('h:i:s');
  $mailer->send($message);
echo date('h:i:s') . "\n";

  $ne++;
  echo "</br>n:".$ne."&nbsp".$user["email"]."</br> >>enviado</br>";

Answer 1

You’re probably talking about ob_implicit_flush. Yes, it is possible to display an output in php even while running a loop, without waiting for that loop to be finished. That is, the data is printed in a stack.

ob_implicit_flush(true);


foreach (range(1, 50) as $value)
{
    echo "Imprimindo {$value}";
    ob_flush();

    sleep(1);
}

My php.ini is configured to automatically start a buffer.

If you don’t know whether your output buffer is automatic or not in your php.ini, you can do this little check to make sure everything works properly.

if (ob_get_level() > 0) { 
    ob_start();
}

While complementing the answer, you can do this by just using the function flush, provided you are not using anything related to output buffer in your code.

So you can do it like this:

// Fallback para garantir que não vai ter a configuração no php.ini

while(ob_get_level() > 0) ob_end_clean();    

foreach (range(1, 50) as $value)
{
    echo "Imprimindo {$value}";
    flush();

    sleep(1);
}

I tested both ways and worked perfectly on my machine.

Answer 2

There are several techniques that may or may not work according to the environment.

Here’s a slightly different example from the one already posted:

ini_set('zlib.output_compression', 0);
ini_set('implicit_flush', 1);
ob_end_clean();

echo 'Hello World!';
flush();
ob_flush();

for ($i = 1; $i < 6; $i++) {
    sleep(1);
    echo PHP_EOL.'<br />'.$i;
    flush();
    ob_flush();
}

The only difference is that in this example we disable the compression zlib, which is normally activated by default.

Important also that we are using ob_end_clean() before starting processes to ensure that any existing output buffer is deleted.

It does not necessarily need to be placed in the first line of codes. Just be before the initial logic of the buffer script you want to work with.

One problem you may have in this example above is that the last link does not respect the sleep(1), because it prints right after the penultimate. But this behavior does not happen in certain environments.

It is very complicated to hit something that works 100%. There is no magic that makes it work consistently in every type of environment. You have to test and adapt to your specific case.