I wanted to create a really simple short url service for the permalinks on this website (priteshgupta.com) by using the domain prite.sh.

Here is what I came up with:

<?php
  // Go to a URL like 
  // http://shorturl.com/short?url=https://priteshgupta.com/2016/05/sticky-css-footer/
  // To generate a URL like http://shorturl.com/GwDJ
  $data = file_get_contents('data.json');
  $json = json_decode($data, true);
  $short_url = substr($_SERVER['REQUEST_URI'], 1);

  if ($json[$short_url]) {
    // Cache the redirect in the browser
    header('HTTP/1.0 301 Moved Permanently');
    header("Location: $json[$short_url]");
    header('Cache-Control: private');
    header('Vary: User-Agent, Accept-Encoding');
  } else if ($_GET['q'] === '/short' && $_GET['url']) {
    // Generate the unqiue string for the short url
    function generate_key() {
      $chars = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
      $random_key = '';

      // For this, I am using 4 characters as the length of my short URLs
      for ($i = 0; $i < 4; $i++) {
        // 61 = length of $chars - 1
        $random_key .= $chars[rand(0, 61)];
      }

      return $random_key;
    }

    if (!in_array($_GET['url'], array_values($json))) {
      $url_key = generate_key();

      while (in_array($random, array_keys($json))) {
        $url_key = generate_key();
      }

      $json[$url_key] = $_GET['url'];
      file_put_contents('data.json', json_encode($json, true));
    } else {
      $url_key = array_search($_GET['url'], $json);
    }

    echo "<input onClick='this.select();' readonly='true' value='http://shorturl.com/$url_key' />";
  } else {
    echo 'Read: https://github.com/priteshgupta/ShortURL';
  }

The above PHP code uses a JSON file which would be located in the same folder as this PHP file. This also means that the JSON file needs to be initialized (echo '{}' >> 'data.json') and with the right permissions (chmod 666 data.json <- give every user read + write access).

n.b. Since it doesn’t use a database, but rather reads (and writes) to the JSON file for every operation, this isn’t exactly built to scale.

Additionally, this is the Nginx configuration file I use for routing at prite.sh (the error_page, fastcgi, etc, sections are irrelevant, but I’d rather share the entire file).

server {
  listen 80 default_server;
  listen [::]:80 default_server;

  root /var/www/shorturl/html/;
  index index.php index.html index.htm;

  server_name shorturl.com www.shorturl.com;

  location / {
    try_files $uri $uri/ /index.php?q=$uri&$args;
  }

  error_page 404 /404.html;
  error_page 500 502 503 504 /50x.html;
  location = /50x.html {
    root /usr/share/nginx/html;
  }

  location ~ \.php$ {
    try_files $uri =404;
    fastcgi_split_path_info ^(.+\.php)(/.+)$;
    fastcgi_pass unix:/var/run/php/php7.0-fpm.sock;
    fastcgi_index index.php;
    include fastcgi_params;
  }
}

Source also located at https://github.com/priteshgupta/ShortURL (for ZIP download, etc).