PHP 5 second countdown (CLI, not JavaScript) - php

Question

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 script. How can I do this with PHP?

Answer 1

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;

Answer 2

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";

Answer 3

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!";

Answer 4

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.

Answer 5

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.