Add 'index.php'
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248
index.php
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248
index.php
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<?php
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// Simple URL shortener in a single PHP file
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// by bagaag.com
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// Configuration
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$last_file = 'last.txt'; // file to store the last incremented key
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$urls_file = 'urls.txt'; // file to store the URLs with their keys
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$charset = 'acr8mqbs7di4tuh6e9fjv2gwx0nlk5poy1z3'; // unique set of characters for generating keys
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$max_url_length = 100; // urls longer than this are considered nefarious
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$allowed_domains = []; // list of allowed domains for URL shortening
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$password = 'change me!'; // password to shorten a URL, leave empty to disable password protection
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$enable_test = false; // enable the test function to output a series of incremented keys
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// Returns the contents of $last_file, or empty string if the file does not exist
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function get_last() {
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global $last_file;
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if (file_exists($last_file)) {
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return trim(file_get_contents($last_file));
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}
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return '';
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}
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// Writes to $last_file
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function set_last($s) {
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global $last_file;
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file_put_contents($last_file, $s);
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}
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// Provides the next key by incrementing the previous key.
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// Start with empty string and then feed the return value
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// back into this function to get the next key, and repeat.
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function increment_string($s) {
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global $charset;
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// convert the charset to an array of characters
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$chars = str_to_chars($charset);
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// if the string is empty, return the first character
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if ($s === '') {
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return $chars[0];
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}
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// convert the input string to an array of characters
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$string = str_to_chars($s);
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// iterate over the input string characters from end to beginning
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for ($index = count($string) - 1; $index >= 0; $index--) {
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// find and validate the position of the character in the charset
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$char = $string[$index];
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$pos = array_search($char, $chars);
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if ($pos === false) {
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return "Character not in set: $char";
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}
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// if the character is not the last in the charset, increment it and break
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if ($pos < count($chars) - 1) {
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$string[$index] = $chars[$pos + 1];
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break;
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}
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// character is the last in the charset; wrap around to the first character
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$string[$index] = $chars[0];
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// if we are at the beginning of the string, prepend the first character and break
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if ($index === 0) {
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array_unshift($string, $chars[0]);
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break;
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}
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}
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return join('', $string);
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}
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// Splits a string into an array of characters
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function str_to_chars($str, $l = 0) {
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if ($l > 0) {
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$ret = array();
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$len = mb_strlen($str, "UTF-8");
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for ($i = 0; $i < $len; $i += $l) {
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$ret[] = mb_substr($str, $i, $l, "UTF-8");
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}
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return $ret;
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}
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return preg_split("//u", $str, -1, PREG_SPLIT_NO_EMPTY);
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}
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// Reads the last key, increments it, saves it, and returns it
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function next_key() {
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$last = get_last();
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$next = increment_string($last);
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set_last($next);
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return $next;
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}
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// Adds a URL to urls.txt and returns the generated key
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function add_url($url) {
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global $urls_file;
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$key = next_key();
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// append the key and url to urls.txt
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file_put_contents($urls_file, $key . ' ' . $url . "\n", FILE_APPEND);
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return $key;
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}
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// Looks up a key in urls.txt and returns the corresponding URL, or null if not found
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function get_url($key) {
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global $urls_file;
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$lines = file($urls_file, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
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foreach ($lines as $line) {
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list($k, $url) = explode(' ', $line, 2);
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if ($k === $key) {
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return $url;
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}
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}
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return null;
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}
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// Test function to print a series of incremented keys
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// Usage: output_keys('', 100);
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function output_keys($key, $count) {
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header('Content-Type: text/plain');
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for ($i = 0; $i < $count; $i++) {
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$key = increment_string($key);
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// set content type to plain text
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print($key . "\n");
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}
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}
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// Get input either from a GET or POST request
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function get_input($name) {
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if (isset($_POST[$name])) {
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return $_POST[$name];
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} elseif (isset($_GET[$name])) {
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return $_GET[$name];
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}
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return null;
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}
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// Test if a host is in the allowed domains list
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function test_host($host) {
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global $allowed_domains;
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if (empty($allowed_domains)) {
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return true; // if the list is empty, allow all domains
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}
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return in_array($host, $allowed_domains);
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}
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/* HTTP Request Handling */
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// read input parameters
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$url = get_input('url');
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$input_password = get_input('password');
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$key = get_input('key');
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$test_start = get_input('test_start');
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$test_count = get_input('test_count');
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// If a URL is provided, attempt to shorten it
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if ($url) {
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// if a password is set, check it
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if ($password !== '' && $input_password !== $password) {
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http_response_code(401); // Unauthorized
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echo "Unauthorized: Incorrect password.\n";
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exit;
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}
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// return 422 if the URL is longer than max_url_length
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if (strlen($url) > $max_url_length) {
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http_response_code(422); // Unprocessable Entity
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echo "Invalid URL.\n";
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exit;
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}
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// return 403 if the URL's domain is not in the allowed list
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$parsed_url = parse_url($url);
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if ($parsed_url === false || !isset($parsed_url['host']) || !test_host($parsed_url['host'])) {
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http_response_code(403);
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echo "Forbidden: This URL is not within the list of allowed domains.\n";
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exit;
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}
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// validate the URL and shorten it
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if (filter_var($url, FILTER_VALIDATE_URL)) {
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$key = add_url($url);
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$shortened_url = "https://$_SERVER[HTTP_HOST]/$key";
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echo "$shortened_url\n";
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} else {
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http_response_code(422); // Unprocessable Entity
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echo "Invalid URL.\n";
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}
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exit;
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}
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// If test parameters are provided, output a series of incremented keys
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if ($enabed_test && $test_start !== null && $test_count !== null) {
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// validate password
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if ($password !== '' && $input_password !== $password) {
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http_response_code(401); // Unauthorized
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echo "Unauthorized: Incorrect password.\n";
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exit;
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}
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output_keys($test_start, (int)$test_count);
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exit;
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}
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// Otherwise, assume the request URI is a key to look up
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$path = parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH);
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$key = trim($path, '/');
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// If the key is valid, look up the URL and redirect
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if ($key !== '') {
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$url = get_url($key);
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if ($url !== null) {
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header("Location: $url", true, 301);
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exit;
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} else {
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http_response_code(404);
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echo "Not Found.\n";
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exit;
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}
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}
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// If no key or url is provided, show a simple HTML form to submit a URL
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?>
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8">
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<title>Bagaag.com Micro URL Shortener</title>
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</head>
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<body>
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<h1>Bagaag.com Micro URL Shortener</h1>
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<form method="post" action="">
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<label for="url">Enter URL to shorten:</label><br>
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<input type="text" id="url" name="url" size="50" required><br><br>
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<?php if ($password !== ''): ?>
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<label for="password">Enter the password:</label><br>
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<input type="password" id="password" name="password" size="20" required><br><br>
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<?php endif; ?>
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<input type="submit" value="Shorten">
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</form>
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<?php if ($enable_test): ?>
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<h2>Test Key Generation</h2>
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<form method="post" action="">
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<label for="test_start">Generate keys from:</label><br>
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<input type="text" id="test_start" name="test_start" size="50" placeholder="Leave blank to start from beginning"><br><br>
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<label for="test_count">How many keys to generate:</label><br>
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<input type="text" id="test_count" name="test_count" size="10" required><br><br>
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<?php if ($password !== ''): ?>
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<label for="password">Enter the password:</label><br>
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<input type="password" id="password" name="password" size="20" required><br><br>
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<?php endif; ?>
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<input type="submit" value="Generate">
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</form>
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<?php endif; ?>
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</body>
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</html>
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