index.php

<?php
/*~ Greco395 Simple Url Shorter
.---------------------------------------------------------------------------.
|  Software: Simple Url Shorter                                             |
|   Version: 0.9.1                                                          |
|      Site: https://greco395.com/                                          |
| ------------------------------------------------------------------------- |
|    Author: Greco Domenico (project admininistrator & Author)              |
|   Founder: Greco395.com                                                   |
| ------------------------------------------------------------------------- |
| This program is distributed in the hope that it will be useful - WITHOUT  |
| ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or     |
| FITNESS FOR A PARTICULAR PURPOSE.                                         |
'---------------------------------------------------------------------------'
*/

//////// CHANGE THE FOLLOWING VARIABLES /////////

// Website URL ( add the "/" at the end )
$website_name = "http://example.com/";

// Database configuration
$dbHost     = "db_host";
$dbUsername = "db_user";
$dbPassword = "db_pass";
$dbName     = "db_name";

////////////////////////////////////////////////


// Create database connection
try{
    $db = new PDO("mysql:host=$dbHost;dbname=$dbName", $dbUsername, $dbPassword);
}catch(PDOException $e){
    echo "Connection failed: " . $e->getMessage();
}


class URL_SHORTER{
    public $domain;
    protected static $chars = "abcdfghjkmnpqrstvwxyz|ABCDFGHJKLMNPQRSTVWXYZ|0123456789";
    protected static $table = "short_urls";
    protected static $checkUrlExists = false;
    
    public function __construct(){
        global $website_name;
        $this->domain = $website_name;
    }
    public function validateUrl($url){
        if (strpos($url, $this->domain) !== false) {
    		return false;
		}
        return filter_var($url, FILTER_VALIDATE_URL, FILTER_FLAG_HOST_REQUIRED);
    }
    public function checkUrl($url){
        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_NOBODY, true);
        curl_setopt($ch,  CURLOPT_RETURNTRANSFER, true);
        curl_exec($ch);
        $response = curl_getinfo($ch, CURLINFO_HTTP_CODE);
        curl_close($ch);

        return (!empty($response) && $response != 404);
    }
    function urlExistsInDB($url){
        global $db;
        $query = "SELECT short_code FROM ".self::$table." WHERE long_url = :long_url LIMIT 1";
        $stmt = $db->prepare($query);
        $params = array(
            "long_url" => $url
        );
        $stmt->execute($params);

        $result = $stmt->fetch();
        return (empty($result)) ? false : $result["short_code"];
    }
    public function generateRandomString($length = 6){
        $sets = explode('|', self::$chars);
        $all = '';
        $randString = '';
        foreach($sets as $set){
            $randString .= $set[array_rand(str_split($set))];
            $all .= $set;
        }
        $all = str_split($all);
        for($i = 0; $i < $length - count($sets); $i++){
            $randString .= $all[array_rand($all)];
        }
        $randString = str_shuffle($randString);
        return strtoupper($randString);
    }
    public function insertUrlInDB($url, $code){
        global $db;
        $query = "INSERT INTO `short_urls` (`id`, `long_url`, `short_code`, `hits`, `created`) VALUES (null,	'".$url."',	'".$code."',	0,	".time().");";
        $stmnt = $db->exec($query);
        return $db->lastInsertId();
    }
    public function infoID($id){
        global $db;
        $stmt = $db->prepare("SELECT * FROM short_urls WHERE id=?");
        $stmt->execute([$id]); 
        return $stmt->fetch();
    }
    public function shortize($long_url){
        if(isset($long_url)){
            $isset_urlDB = self::urlExistsInDB($long_url);
            if($isset_urlDB != true){
                if(self::checkUrlExists == true){
                    if($this->checkUrl($long_url) != true){
                        return "INVALID WEBSITE";
                    }
                }
                if($this->validateUrl($long_url)){
                    return $this->domain.self::infoID(self::insertUrlInDB($long_url, self::generateRandomString(4)))['short_code'];
                }else{
                    return "INVALID URL";
                }
            }else{
                return $this->domain.$isset_urlDB;
            }
        }
        
    }
}
$shorty = new URL_SHORTER;

// REDIRECT SHORT URL TO LONG URL
if(isset($_GET) && !isset($_GET['new'])){
    foreach($_GET as $rq){
        if(strlen($rq) < 5 && strlen($rq) > 3){
            header("Location: ".$shorty->infoCODE($rq)['long_url']."");
        }
    }
}



// EXAMPLE
//  echo $shorty->shortize("https://greco395.com");
//