PHP虽然条件

Question

I'm trying to learn PHP and I wrote this code:

<?php

$number = 1;

while ($number < 21)
{
    echo "<p>I'm  " . "$number" . " years old!</p>";
    $number++;
}

?>

So my question is; is it possible to set-up something to see the sentences appear after a couple of seconds? Like this, first you see: I'm 2 years old!, then after like 3 seconds: I'm 3 years old! appears, then after another 3 seconds: I'm 4 years old! appears. Is that possible? Btw this is my first post, if I made a mistake please give feedback, it would help me in the future :)

Thank you

EDIT for possible future visitors: PHP isn't designed for this, but javaScript is.

Answer 1

PHP is a server side scripting language, and the code executes on server side. The final produced text is sent to the client as is and shown in the browser. If you want to animate the text or delay a couple of seconds, this has to be done in the client side, using Javascript (and NOT PHP).

The javascript for something like that would look like that:

var n = 1;
a = setInterval(function() {
    document.write("I'm " + n + " years old!");
    if (n++ >= 21) {
        clearInterval(a);
    }
}, 1000);

The client side would execute Javascript from what PHP sends, so if we send some Javascript code inside a <script> tag from PHP, it will be executed in the client side. So, we can do:

<?php
    echo "<script type='text/javascript'>var n = 1; a = setInterval(function() { document.write('I\'m ' + n + ' years old!'); if (n++ >= 21) clearInterval(a); }, 1000);</script>";
?>

Of course you don't really have to use PHP for that (you can just include the Javascript code inside a <script> tag and outside of <?php ?> tags, and it will be evaluated in the client side and not on the server side.