how to delete all cookies of my website in php

PHP setcookie()

Taken from that page, this will unset all of the cookies for your domain:

// unset cookies
if (isset($_SERVER['HTTP_COOKIE'])) {
    $cookies = explode(';', $_SERVER['HTTP_COOKIE']);
    foreach($cookies as $cookie) {
        $parts = explode('=', $cookie);
        $name = trim($parts[0]);
        setcookie($name, '', time()-1000);
        setcookie($name, '', time()-1000, '/');
    }
}

http://www.php.net/manual/en/function.setcookie.php#73484

$past = time() - 3600;
foreach ( $_COOKIE as $key => $value )
{
    setcookie( $key, $value, $past, '/' );
}

Even better is however to remember (or store it somewhere) which cookies are set with your application on a domain and delete all those directly.
That way you can be sure to delete all values correctly.

I agree with some of the above answers. I would just recommend replacing "time()-1000" with "1". A value of "1" means January 1st, 1970, which ensures expiration 100%. Therefore:

setcookie($name, '', 1);
setcookie($name, '', 1, '/');

The provided Answers did not solve my problem,

It did not:

1. Remove parent domain cookies (from a.b.c; remove b.c; cookies),
2. Remove cookies from a higher path other then root.

My script does, see.

<?php function unset_cookie($name)
{
    $host = $_SERVER['HTTP_HOST'];
    $domain = explode(':', $host)[0];

    $uri = $_SERVER['REQUEST_URI'];
    $uri = rtrim(explode('?', $uri)[0], '/');

    if ($uri && !filter_var('file://' . $uri, FILTER_VALIDATE_URL)) {
        throw new Exception('invalid uri: ' . $uri);
    }

    $parts = explode('/', $uri);

    $cookiePath = '';
    foreach ($parts as $part) {
        $cookiePath = '/'.ltrim($cookiePath.'/'.$part, '//');

        setcookie($name, '', 1, $cookiePath);

        $_domain = $domain;
        do {
            setcookie($name, '', 1, $cookiePath, $_domain);
        } while (strpos($_domain, '.') !== false && $_domain = substr($_domain, 1 + strpos($_domain, '.')));
    }
}

It is not the most pretty/safe/optimal solution, so use this only if you do not known the cookie-path and/or cookie-domain's. Or use the idea in order to create your version.