当sleep（）和usleep（）给我一个Error 500时，如何在PHP中暂停？

Question

(For you nosy people): I'm designing a Utopian English assignment for school, I asked my teacher if I could create a website instead of a brochure.

Anyways, I'm trying to get a pause in between a "while" loop. I've tried sleep() and usleep(), they just give me an error 500. I am trying to change the title of the webpage every five seconds between variable $a and variable $b. I've tried the following:

echo '<title>'.while (true) {.$a.sleep(5).$b.sleep(5)}.'</title>';

and

while (true) {
    echo '<title>'.$a.'</title>';
    sleep(5)
    echo '<title>'.$b.'</title>';
}

Answer 1

I think you are mixing something up here: PHP is processed on the server side which means the user won't see anything until the server is completely done with interpreting the page. what you are doing is basically telling the server to write <title>$foo</title> for an infinite amount of time.

To accomplish what you are trying to do you need to write the logic in javascript (which is interpreted on the client side). It would look something like this:

var i = 0;
function toggleTitle() {
    if(i % 2 == 0) {
        document.title = "foo";
    }
    else {
        document.title = "bar";
    }
    i++;
}

setInterval(toggleTitle, 5000);