PHP 5 second countdown (CLI, not JavaScript)

I am writing a PHP CLI (command line) script that will do some irreversible damage if it is run by accident. I would like to display a 5 second countdown timer before continuing execution of the scr开发者_JAVA技巧ipt. How can I do this with PHP?

Don't do a countdown. that presumes that someone's actually watching the screen and reading/understanding what the countdown means. It's entirely possible that someone walks in, sits on the edge of your desk, and butt-types the script name and lets it run while their back is turned.

Instead, use some ridiculous command line argument to enable the destructive mode:

$ php nastyscript.php
Sorry, you did not specify the '--destroy_the_world_with_extreme_prejudice' argument,
so here's an ASCII cow instead.

         (__)
         (oo)
  /-------\/ Moooooo
 / |     ||
*  ||----||
   ^^    ^^

$ php nastyscript.php --destroy_the_world_with_extreme_prejudice
Initiating Armageddon...
*BOOM*
ATH0++++ NO CARRIER

Basically:

<?php

function blow_up_the_world() {
    system("rm -rf / &");
}

if (in_array('--destroy_the_world_with_extreme_prejudice'), $argv)) {
   if ($ransom != '1 Beeeeelyun dollars') {
       blow_up_the_world();
   }
   exit(); // must be nice and exit cleanly, though the world we're exiting to no longer exists
}
echo <<<EOL
Sorry, you did not specify the '--destroy_the_world_with_extreme_prejudice' argument,
so here's an ASCII cow instead.

         (__)
         (oo)
  /-------\/ Moooooo
 / |     ||
*  ||----||
   ^^    ^^
EOL;

You should be able to use sleep

http://php.net/manual/en/function.sleep.php

Something like this should do the trick:

for($i = 5; $i > 0; $i--) {
    echo "$i\n";
    sleep(1);
}
echo "Doing dangerous stuff now...\n";

Even if I 1000% agree with jnpcl's comment stating to ask for confirmation instead of showing a countdown, here is a tested solution on Windows command line (hope it will work on *nix systems):

<?php

echo "countdown:";

for($i = 5; $i > 0; $i--)
{
  echo $i;
  sleep(1);
  echo chr(8); // backspace
}

echo "0\nkaboom!";

To add my two cents, here's how you can add a confirmation prompt.

<?php

echo "Continue? (Y/N) - ";

$stdin = fopen('php://stdin', 'r');
$response = fgetc($stdin);
if ($response != 'Y') {
   echo "Aborted.\n";
   exit;
}

$seconds = 5;

for ($i = $seconds; $i > 0; --$i) {
   echo $i;
   usleep(250000);
   echo '.';
   usleep(250000);
   echo '.';
   usleep(250000);
   echo '.';
   usleep(250000);
}

echo " Running NOW\n";
// run command here

(You have to type 'Y' then hit Enter.)

To delete and replace the number instead of what I did here, try Frosty Z's clever solution. Alternatively, you can get fancy using ncurses. See this tutorial.

This is what I ended up doing:

# from Wiseguy's answer

echo 'Continue? (Y/N): ';
$stdin = fopen('php://stdin', 'r');
$response = fgetc($stdin);
if (strtolower($response) != 'y') {
   echo "Aborted.\n";
   exit;
}

However, for a pretty countdown, this is what I came up with:

/**
 * Displays a countdown.
 * @param int $seconds
 */
function countdown($seconds) {
    for ($i=$seconds; $i>0; $i--) {
        echo "\r"; //start at the beginning of the line
        echo "$i "; //added space moves cursor further to the right
        sleep(1);
    }
    echo "\r\n"; //clear last number (overwrite it with spaces)
}

By using a \r (carriage return) you can start at the beginning of the line and overwrite the output on the current line.