PHP ob_start & flush - print and clean text in loop

Question

Is it possible to print text on the screen using ob_start() & flush() and finally clean this text?

Now I have something like that:

<?php
ob_start();

ob_end_flush(); flush(); ob_flush();
for($i = 0; $i<100; $i++)
{
    echo $i.'<br>';
    flush();
    ob_flush();
}

ob_end_flush();
?>

and when I execute this code, I get something like that:

0
1
2
3
4
5
6
7
8
...

But I want echo current key and clean them:

0
... (clean "0")

1
... (clean "1")

2
... (clean "2")

Finally I would like to have only one number on the screen. Is it possible in PHP?

Thanks.

Answer 1

Going by the comments of OP, I'm going to assume OP wants a timer on the command line and presume the <br> was meant to convey a newline.

A timer on the command line, which clears the line every tick, could be construed as follows:

for( $i = 0; $i < 100; $i++ ) {
  /*
    the \r moves the cursor back to the start of the line
    the additional spaces are there to make sure 
    any additional digits are removed as well
    adjust the amount of spaces to the max amount of digits
    (which is actually only useful if the timer was counting down, in stead of counting up)
  */
  echo "$i  \r";
  // wait a second
  sleep( 1 );
}

ob_* functions are of no use here; they are merely meant as an internal buffer for PHP, before it sends the output. You can't clear what's already been sent out.

If you want to completely clear the screen as well, I suggest to look at the suggestions in this question and related questions.

However, if you are outputting through a web server and viewing the result in a web browser, you are out of luck. You can't clear the output you have sent to a web browser, in the way you intend, because the web is a client <-> server architecture. You'll have to understand this architecture and use something like AJAX, websockets, or perhaps long polling.

Answer 2

If you need to do it in console, @Decent Dabbler showed best suggestion. If you need to do it in the browser, you don't need PHP. You can make in using javascript.

function setCounter(value)
{
  document.getElementById('counter').innerText = value;
}

var counter = 0;
setInterval(
  function() {
    setCounter(++counter);
  },
  1000
);

<div id="counter"></div>

Answer 3

The solution is like e-commerce and basket and cookie and 99 times go request and answer between client and server. After every $i must have exited, and again request with the cookie and $i+1. And all like that to the end of looping.

Maybe this is what you want. On screen is only one number, last one, 99.

<?php
    ob_start();

    for($i = 0; $i<100; $i++)
    {
        echo $i.'<br>';  
        //flush();
        //ob_flush();
        ob_clean();
        echo $i.'<br>';
    }

    ob_end_flush();
    ?>